Vacuum contactor operation with parallel connection of independent consumers

Description:     Vacuum contactor operation with parallel connection of independent consumers     This work presents a model of a transformer substation with parallel connection of independent consumers via vacuum switches. Several options of an electric arc model are considered upon switching off a vacuum switch such as: KEMA model and "black box" model. Modern computer models of vacuum switches were analyzed. Since the model data were not suitable for the conditions of the experiment, a simulation computer model was developed that reflects the specifics of the operation of the substation and of the transition process upon disconnection of one or several vacuum switches. The results of the developed methodology of analyzing transition processes were verified. To check the results of computer simulation, an experimental model was constructed, it consisted of: an electric load (inductive nature), a power supply, two vacuum switches, and a measuring circuit. The circuit is switched on and off using a pneumatic system controlled by a microcontroller. The primary purpose of the work is to check mutual influence of vacuum switches upon parallel disconnection, since there may be a restrike caused by effects of switching overvoltage between neighboring switches upon irregular disconnection. The effects of a transition process in one switch on the total current of the entire system were identified. A stand for a projected trial was demonstrated as well.     With continuing development of science and technology, high voltage electrical equipment performance has been improved very fast, and dashed out some of the new switch gear, for example, the F-C circuit. Through understanding and analyzing the principle, characteristic and function, etc of F-C circuit , describes its advantages in some areas relative to the circuit breaker, For example, the protection of a more timely, overvoltage lower, functions in line with more reasonable; the lower cost for. Purpose is to allow engineers to correct reasonable selection of high voltage switch when used in the design and to promote domestic F-C circuit development.     The design, operation and use are characterized for high voltage vacuum contactors in underground coal mines endangered by methane and coal dust explosions. Design of a vacuum contactor is shown in a scheme. Vacuum contactors are superior to electromagnetic contactors. Vacuum contactors have a reduced size and weight and are characterized by improved commutation properties. Under vacuum conditions, intensity of electric discharges is lower than in an electromagnetic contactor. Reliability of vacuum contactors is 16 to 20 times higher than that of electromagnetic contactors (90% of metal vapors caused by an electric arc settle on contact surface). No time consuming buildup removal or cleaning is necessary. Optimizing contactor position in a power system in underground mines is discussed. Efficiency of using vacuum contactors and the RC systems is discussed.     Vacuum contactor is an electrically controlled switch that is used to make or break an electrical circuit with the help of vacuum interrupter, relay, and fuse. The drivers of the this market are influenced by the trends in the commercial sector and by the trends in the process and manufacturing industry. Growth in the related as well as complementary markets, such as motors, capacitors, switchgear, and transformer, also contribute towards the growth of vacuum contactors.     The global vacuum contactor market size is estimated to reach $4,814.6 Million by 2020 from $3,426.8 Million in 2015. Vacuum contactor is an electrically controlled switch that is used to make or break an electrical circuit with the help of vacuum interrupter, relay and fuse. It is mainly found in motor starters, switchgear and control gear of medium voltage fast switching devices.  The drivers of the high voltage vacuum contactormarket are influenced by the trends in the process industries, manufacturing industries, commercial and large residential sectors that use HVAC systems.     This market study covers medium voltage vacuum contactors of various voltage ratings, applications, and end-users for arriving at the global market size from 2013 to 2020. In terms of voltage rating, the vacuum contactor market is segmented into four divisions: less than 5kV, 5-10 kV, 10-15 kV and more than 15kV.     On the basis of application the vacuum contactors market is classified into six segments: motors, transformers, capacitors, reactors, resistive loads and others (such as generators, pumps, variable frequency drives, feeders, power transmitters and switchgears). Motors, transformers and capacitors are the top three applications of this industry that covers more than 65% market share.     On the basis of end-use, the vacuum contactor market is segmented into six sectors: utilities, industrial, commercial, mining, oil & gas and other medium voltage end-users. The other sector includes marine, water & waste water pumping, street lighting and transportation sector.     In terms of region, the single phase vacuum contactor is segmented on the basis of its market presence in the following regions namely North America, South America, Europe, Asia-Pacific and Middle East & Africa. These regions are further classified on the basis of top countries and their end user analyses have been made. Asia-Pacific held the largest market share owing to growth in industrialization and urbanization, followed by Europe and North America.     The global vacuum contactor market is projected to witness high growth on account of rising energy demand, growing commercial and industrial sector, and increased up-gradation of electrical infrastructure. The market was valued at $3,210 Million globally in 2014 and is projected to grow at a CAGR of 7.04% from 2015 to 2020.     The Asia-Pacific region holds a majority of market share owing to urbanization and significant development in process industries such as paper & pulp, cement, metal processing industries, and growth in manufacturing industries, followed by North America and Europe. In terms of individual countries, the U.S. and China show high growth potential. This growth can be attributed to the increasing demand for reliable power and investments for replacing aging T&D infrastructure in the U.S. and progressive economic growth of China.     Amongst the end-users, utilities sector is estimated to hold the major market share owing to increasing installation of power infrastructure. North American region is currently focussing on grid modernization and replacement of existing power infrastructure. Few countries in Europe are shifting towards renewable sources for power generation that has boosted the low voltage vacuum contactor market in the region. Vacuum contactor finds vast application in industrial and commercial sectors as well.     In terms of growth strategies, market players have mainly been forming mergers and acquisitions in order to expand as well as strengthen their market foothold. Contracts & agreements is the most commonly adopted strategy that is followed by mergers & acquisitions, and expansions. This shows a mix of both organic and inorganic growth strategies.     Leading players in the industry, based on their recent developments and other strategic industrial activities, include ABB Ltd. (Switzerland), Eaton Corporation Plc. (Ireland), Mitsubishi Electric Corporation (Japan), Schneider Electric SE (France), and Siemens AG (Germany).     With continuing development of science and technology, high voltage electrical equipment performance has been improved very fast, and dashed out some of the new switch gear, for example, the F-C circuit. Through understanding and analyzing the principle, characteristic and function, etc of F-C circuit , describes its advantages in some areas relative to the circuit breaker, For example, the protection of a more timely, overvoltage lower, functions in line with more reasonable; the lower cost for. Purpose is to allow engineers to correct reasonable selection of high voltage switch when used in the design and to promote domestic F-C circuit development.

Publish Date: 2021/08/19

What are Flight Cases?

Description:     What are Flight Cases?     Flight cases, carrying cases or equipment cases are sturdy, rigid trunks or enclosures designed for protecting personal goods in transit and storage. They’re typically made from plastic or metal. Many models feature a range of additional options, like heavy-duty foam inserts or additional protective padding.     High-end transit equipment cases are widely used in a range of demanding industries and roles. This includes the avionics, transport, electronic, entertainment, photography and video, test and measurement, medical, security and military sectors, to name just a few.     Flight cases are primarily designed to shield and protect fragile or high-value items during transit. Some are specifically designed to house particular pieces of equipment or instruments. Others are more adaptable and can be used to protect almost any important goods that may otherwise be at risk of damage.     Because they’re chiefly used as a handy solution for long-distance travel, long-term storage or frequent location changes, rack flight case are also commonly known as shipping cases or transportation cases. You will sometimes see them referred to as roadie cases, as they make a popular solution for conveying musical instruments and technical equipment between different locations.Flight cases can be used to store, protect and transport a wide variety of equipment types and tools, depending on which sort of case you choose. As mentioned above, musical instruments are one of the common types of flight case hardware, but you will find all sorts of items being shipped in these robust, heavy-duty enclosures.     Flight Cases for Guitars     Flight cases for guitars are a popular choice among musicians. Many such equipment or roadie cases are specially designed to provide added protection for guitars in transit. Both acoustic and electric guitars require careful handling during shipping or air travel. Their weight, size, and relative fragility mean that they are prone to damage, and this is why protection with a quality flight case during a trip is essential.     Guitar flight cases tend to be built in such a way as to provide additional support and padding around the most vulnerable parts of the instrument. These normally include both the headstock and neck of the guitar, particularly at key joints and where cutaways on the body taper sharply.     You’ll often see flight cases intended specifically for travel with guitars that include a good deal of strong secondary bracing, packing or foam padding at these vital points. They’re usually designed to provide reliable cushioning and support around the bridge and headstock of the instrument. Additional reinforcement is sometimes focused on areas where the main sections of the head, neck and body join together.     Guitar flight cases are often made from fairly lightweight but sturdy materials, such as rigid plastic or aluminium. This generally provides a good level of overall protection, while also being more convenient to carry between locations. Cases designed for shipping multiple guitars together often include built-in racking systems. These typically come with wheels for easier manoeuvring on the ground.     Flight Cases for Guitar Amps     Just as with guitars themselves, flight cases for guitar amps are another important piece of kit for many travelling musicians and road crews.     A guitar amp flight case can come in many sizes and configurations, depending on the type and size of amp or speaker you need to pack up safely ready for shipping. Again, they tend to focus on delivering robust knock and fall protection, with heavy padding on the interior.     Like many such equipment cases, they’re often made from high-grade plastic or metals like cast aluminium. Their bodies may be ribbed for further strength and rigidity, offering an ideal combination of strength and a lighter carry weight for travel.     Additional features can include:     Sturdy comfort grip handles with increased lift capacities     Retaining straps     Toggle catches with wire seals and padlock facilities     Rubber seals for better waterproofing     Stacking locators in the lid, to help when you need to pack or store more than one crate together     Flight Cases for Drums     Flight cases for drums are also a popular choice as proper storage and transportation of drumkits is equally important. It’s particularly vital to protect drum kits in transit as their large size and hollow construction can leave them extremely vulnerable to damage if they are not properly protected.     The best drum and cymbal flight case options generally tend to include many similar features to guitar and amp lighting&speaker flight case. Look out for benefits such as watertight, airtight and crushproof certifications. These offer reassurance that the case will guard against damage from knocks or falls, water, humidity, and prolonged exposure to heat.     Additionally, some models may even offer functions such as an automatic pressure purge valve. This helps to ensure the shifting forces acting on delicate instruments during air travel remain balanced within safe limits.     Production Flight Cases     Production flight cases and equipment containers also include a wide range of products suitable for shipping important and valuable tech between locations. Common examples include mixer flight cases or sound desk flight cases.     As with all such items, you’ll usually want to look for a robust plastic or aluminium model. Rugged body reinforcement and a good amount of interior shock proofing provided by thick foam inserts are also important.     When buying flight cases for mixers, it’s vital to look out for designs offering features that directly benefit electronics in transit. Waterproof models are particularly popular for shipping mixers, PAs and other production equipment. Shop for cases with sturdier rubber seals and secure fastening/locking systems, helping to guard delicate electronics from humidity, moisture, dust and debris.     Padlock compatibility is another common feature for production flight cases. This makes the cases more secure and helps to prevent unauthorised access to the contents.     Different Flight Case Types     Flight Case Racks     A flight case rack can be extremely important when shipping multiple items together in the same crate or equipment box. Case racks may be integrated into some designs, often called rackmount flight cases. Alternatively, racks can be purchased as an additional accessory designed to fit inside an existing transit case.     Plastic or metal equipment containers featuring two or more racks are available for both larger and smaller items. These can include various types of electronic equipment, organised spaces for securing different tools, or any other fragile items that need to remain protected and separated during travel.     Quality rackmount flight cases often feature benefits such as panel-mounting capabilities for creating more robust compartments, with shock-mounted rack sleeving and suspension systems for added impact guard.     They make an ideal solution when used as a server flight case, as they’ll often allow for multiple units to be organised and shipped together. This helps you to keep track of exactly which components should be kept together. It also makes reassembly of servers and other computing or electronics arrays much easier when you reach your destination.     Lightweight Flight Cases     Since the items being stored and transported in equipment cases tend to be too large or heavy to carry easily outside of a case, the last thing you want is for the container itself to add a huge amount of bulk to the overall package.     Many of the best lightweight flight case options tend to be made from sturdy plastic or cast aluminium. These materials offer an ideal balance of strength, rigidity and durability while being easy to pick up and move around.     You may also be surprised at the manoeuvrability of some of the larger light flight cases. These also tend to be easily stackable when not in use. Some models even feature stacking locators embedded into their secure-latching lids to make the job even more straightforward.     Hard Carry Cases     Transporting delicate items like laptops or test equipment is an increasingly common necessity. In situations like this, hard carry cases are often chosen for travel with smaller individual pieces of technology or electronics equipment.     Equipment carrying cases are designed to hit the ideal middle ground between portability and protection. This type of hard carrying case tends to be constructed from lighter materials, with prominent easy-grip handles. They also commonly feature a range of additional locking, latching and security measures.     Useful features on cases in this category tend to include IP-rated rubber seals for all-round moisture and dirt protection, and various types of secure latching or locking systems. Whether you opt for a metal or plastic hard carrying case, other handy benefits might include:     Sturdy plug-in lid hinges     Stable and robust case feet     Ergonomic handle designs     High-grade foam inserts for enhanced impact protection Lcd tv flight case with wheels and castors are a popular choice due to their accessibility and ease of movement. Equipment cases with wheels tend to come in several different variants. Firstly, storage boxes with wheels added as an additional convenience tend to have smaller and potentially less sturdy castors and bearings. These are often recessed further into the body of the case, allowing for easier stacking. These models may be less suitable for wheeling over longer distances.     On the other hand, transport cases which feature more prominent wheels often cite full manoeuvrability as a key part of their overall design. This becomes increasingly important with large, heavy or bulky items.     Such models will frequently list features like heavy-duty wheels made from strong materials like polyurethane. Bearings will often be steel or reinforced with other rugged materials and may be self-oiling for smoother free-running action over a wider variety of terrains and surfaces.In addition to protecting against unwanted moisture, waterproof equipment cases also offer a fairly robust level of protection from dust and dirt ingress. When you’re looking for a waterproof hard case, paying attention to the all-important IP rating is key to finding the exact product you need for a particular job or environment. For assistance with this, you can read our comprehensive guide to IP ratings.     Once again, waterproof hard cases can be made from materials such as aluminium and plastic. Certain options are also graded for protection against chemicals, as well as against general environmental hazards such as humidity, rain, spillages and dust.     Regardless of the material you choose, among the most important things to look out for will be thick rubber seals or O-rings around openings, hinges and latches. These will allow you to maintain a watertight (and sometimes completely airtight) interior to your equipment case, even under varying pressures at different altitudes.     Similarly, some models also include automatic one-way pressure release valves. Again, this will help to keep conditions inside the trunk balanced within safe limits at all times.Small flight cases tend to be designed around both portability and protection. This means that they are normally focused on convenience and comfort during journeys, as well as being built sturdily enough to withstand various types of impact, damage or ingress.     Small carrying cases made from aluminium or rigid plastic will also commonly feature some arrangement of foam inserts or padding. This is ideal for protecting less bulky items such as electronics and tools, as well as preventing the contents from moving around too much in transit, and potentially sustaining damage from knocking against the interior of the case.     These smaller cases are less commonly found with wheels attached, as their size usually does not warrant this addition. However, they will often include sturdy feet and a full range of security measures such as latches, locks and wrist straps.Plastic flight cases are a highly popular option. This is due to the impressive combination of ruggedness and low weight offered by modern plastics and polymers. Many of the leading plastic carry cases in the UK and beyond are virtually indestructible under normal transport conditions. Plastic equipment cases offer robust protection against both knocks and impacts, as well as bringing a certain level of water and chemical resistance.     As with all flight case types, plastic equipment boxes can be bought in a wide range of configurations. Advanced IP ratings offer full guarding against moisture, humidity, dust and dirt. Many such products with higher levels of ingress protection will feature thick rubber seals and double-step latching, delivering an extremely reliable performance when closed and secured.Among the most common types of modern metal flight cases are aluminium flight cases with foam inserts. These, alongside other metal flight cases, can be found in widespread use across a huge range of industries and sectors.     Metal Equipment&tool Flight Case are available in both large and small sizes and offer a perfect solution for transporting a huge variety of delicate or high-value goods safely across long distances. Common uses include shipping fragile electronics, instruments and tools.     Lockable metal flight cases with foam padding are highly robust, often featuring reinforced or ribbed cast aluminium side and top panels for added strength. Hinged lids and secure latching mechanisms are frequently coupled with ergonomic comfort grip handles. Wheels or castors tend to be extremely sturdy and smooth-running.     You may notice that many models and types of aluminium flight case are also designed with corners made from toughened, impact-resistant plastic. Not only does this provide extra protection during travel, but it also allows for easier stacking, so you can reduce the amount of storage space needed.     As with all flight cases, metal versions typically include removable PE foam inserts around the walls, base and lid for advanced protection against damage.

Publish Date: 2021/08/19

Numerical Study of Aeroacoustic Sound on Performance of Bladeless Fan

Description:     Numerical Study of Aeroacoustic Sound on Performance of Bladeless Fan     Aeroacoustic performance of fans is essential due to their widespread application. Therefore, the original aim of this paper is to evaluate the generated noise owing to different geometric parameters. In current study, effect of five geometric parameters was investigated on well performance of a Bladeless fan. Airflow through this fan was analyzed simulating a Bladeless fan within a 2 m×2 m×4 m room. Analysis of the flow field inside the fan and evaluating its performance were obtained by solving conservations of mass and momentum equations for aerodynamic investigations and FW-H noise equations for aeroacoustic analysis. In order to design table bladeless fan Eppler 473 airfoil profile was used as the cross section of this fan. Five distinct parameters, namely height of cross section of the fan, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter and aspect ratio for circular and quadratic cross sections were considered. Validating acoustic code results, we compared numerical solution of FW-H noise equations for NACA0012 with experimental results. FW-H model was selected to predict the noise generated by the Bladeless fan as the numerical results indicated a good agreement with experimental ones for NACA0012. To validate 3-D numerical results, the experimental results of a round jet showed good agreement with those simulation data. In order to indicate the effect of each mentioned parameter on the fan performance, SPL and OASPL diagrams were illustrated.     Nowadays, the axial and radial fans are employed for various applications, such as cooling systems, air conditioning, ventilation of underground spaces, etc. The aeroacoustic performance of fans have been improved by increasing advancements in the computational fluid dynamics (CFD) and economic growth, then different types of fans with various applications and higher efficiency is offered. In 2009, a new fan was invented that its appearance and performance was different from conventional fans. The main differences of this fan with respect to conventional fans (axial and radial fans) are the multiplying intake air flow and lack of observable impeller . This fan namely Bladeless/Air Multiplier fan was named on the basis of the two mentioned features. Until now, this fan is manufactured for domestic applications by diameter of 30 cm.     There are two typical fans widely used: axial and radial types, however Bladeless fans are completely distinct from those fans in mechanism aspect. Bladeless fan is similar to centrifugal fans in terms of radial impellers for intake air and also it is similar to axial fans in terms of preparing higher rate of outlet airflow. Although studies about wall and table bladeless fan are rare in the literature, numerous experimental and numerical studies have been performed on the axial and centrifugal fans. Lin, et al , designed a Forward–Curved (FC) centrifugal fan by numerical simulation and experimental tests. They selected NACA 0012 airfoil profile for its blade and indicated that this fan produces a higher maximum flow rate and static efficiency when the blade inlet angle is 16.5o. The influence of enlarged impeller on performance of a centrifugal fan was experimentally examined by Chunxi, et al . By comparison of obtained results, they observed that flow rate, total pressure rise, shaft power and sound pressure level increased while the efficiency of fan decreased for larger blades. Govardhan, et al , investigated the flow field in a cross flow fan by three-dimensional simulation via the commercial software code, CFX. They simulated three impeller geometries for different radius ratio and blade angles, and then they compared their efficiency with each other. Sarraf, et al , experimentally studied axial fans performance for two identical fans but with different impeller thickness. They indicated that the overall performance of these two fans is same, but the fan with thicker blades contained higher rate of pressure loss by the means of 8%. Also the efficiency of the fan with thinner blades was 3% higher than the fan with thicker blade. Mohaideen improved an axial fan blade by using the finite element method (FEM) and reduced 18.5% of the blade weight after optimizing on the blade thickness via stress analysis by ANSYS commercial software.     There are a lot of studies on the generated noise by various airfoils that is carried out by experimental and/or numerical approaches. Chong, et al , measured the generated noise by a 2-D NACA 0012 airfoil at the angles of attack 0o, 1.4o and 4.2o, in a wind tunnel. They performed their experiments for some Reynolds numbers between 1×105 and 6×105. The experimental results indicated that the pressure gradient was raised on the airfoil pressure surface by increasing of attack angle, so the noise can be produced by this phenomenon. Devenport, et al , carried out experimental tests on the noise propagation of NACA 0012, NACA 0015 and S831 airfoil. The obtained results indicated that the airfoils with more thickness made lower noise and revealed the different angles of attack had little influence on the sound production for NACA 0012 and NACA 0015 airfoil. Casper, et al , solved the equations of FW-H and developed new equations. They computed the produced noise by a NACA 0012 airfoil in a low Mach number flow. The analytical results and experimental data for NACA 0012 airfoil were in good agreement.     So far, many experimental and numerical studies have been performed on the generated sound by axial and centrifugal fans. Many researchers have used the FW-H equations to predict the sound radiation of fan by numerical simulation. Ballesteros-Tajadura, et al , measured the noise of a centrifugal fan via FW-H noise model using the CFD code, FLUENT. By comparing numerical and experimental noise results, they showed the FW-H model was able to predict the tonal noise with reasonable accuracy. Solving FW-H equations, Moon, et al and Cho, et al calculated the amount of radiated sound from an axial fan and a cross flow fan, respectively. Younsi, et al , used numerical simulation to predict the noise level in a HVAC forward centrifugal fan. By comparing numerical and experimental data, they showed the good agreement between simulation and the experimental data. In some papers, researchers have studied the source of generating noise in different fans by using the computational aeroacoustics (CAA) . Khelladi, et al , calculated the noise of a high rotational speed centrifugal fan via FW-H analogy and solving the Reynolds Averaged Navier-Stokes (RANS) equations. They compared the numerical and experimental data and also evaluated the aerodynamic performance of fan. In 2009, Sorguven, et al , studied aerodynamic and aeroacoustic performance of two radial fans. Moreover in their study, LES turbulence modeling and FW-H noise modeling were employed. They showed a satisfied agreement of experimental and numerical results and reported FW-H model as a reasonable model for evaluating aeroacoustic performance of fans.     Although Bladeless fan is invented in 2009, but until now aeroacoustic performance of this fan has not been studied numerically or experimentally for different conditions. This fan is designed for home applications by diameter of 30 cm and the only available geometric information is mentioned in patent documentation . In the present study, the effect of five geometric parameters is investigated on performance of a Bladeless fan by diameter 30 cm. The studied parameters are height of fan cross section, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter and aspect ratio for circular and quadratic cross sections. The unsteady conservation of mass and momentum equations are solved to simulate three-dimensional incompressible flow in the Bladeless fan. The Ffowcs Williams and Hawkings (FW-H) formulation is solved to calculate the noise propagation of smart bladeless fan. Firstly, the generated noise of a NACA 0012 airfoil is computed to validate aeroacoustic results by experimental data . The obtained numerical results and the experimental data are in the reasonable agreement, so the FW-H model is employed to measure the tonal noise of Bladeless fan. To validate 3-D numerical simulations, the experimental results of a round jet are compared with numerical simulation results. Since there is not any experimental data about Bladeless fans, round jet is selected due to much similarity. The turbulence in the Bladeless fan is simulated by standard k?ε turbulence model. In order to design cross section of Bladeless fan, Eppler 473 airfoil is chosen among standard airfoils. Eppler 473 airfoil is selected because it is an appropriate airfoil for low Reynolds numbers and high similarity of this airfoil profile to original cross section (designed by inventor) . The volume flow rate is calculated at a distance up to 3 times of nozzle diameter in front of the fan (around 1000 mm) . The numerical results for Bladeless fan show that the investigated parameters in this study are very important to improve the fan performance. Thus these parameters should be considered to design a high performance Bladeless fan.     Mechanism of Bladeless Fan     This fan is produced for domestic applications and its diameter is 30 cm. The mechanism of inlet and outlet airflow from this fan is shown in Fig. 1. At the first stage, the airflow is sucked into the fan through a rotating DC brushless motor and a mixed flow impeller. The intake air is accelerated by passing through an annular aperture which the cross section of this fan is similar to an airfoil profile. Then air is pushed out from a ring shape region, so the air velocity is increased in this region. A considerable pressure difference is generated between both sides of the fan and the discharged air can be described by Bernoulli’s principle. This pressure difference draws the behind and surrounding air toward front of fan. Therefore, a smart tower bladeless fan amplifies the intake air by drawing the air behind and around the fan. Thereby the inventor of this fan claims that this fan multiplies intake air at about 15 times at distance 3D front of fan (around 1000-1200 mm) . All of described stages are shown in Fig.

Publish Date: 2021/08/19

Manufacturing and development of a bolted GFRP flange joint for oil and gas applications

Description:     Manufacturing and development of a bolted GFRP flange joint for oil and gas applications     The manufacturing industry saw a significant rebound, and oil prices started to recover as well. Both of these trends are expected to continue in 2017.     At Allied Valve, we also saw some big changes this year. We expanded our product line to include Masoneilan control valves, CDC rupture discs, and Groth relief valves and flame arresters. We also beefed up our service capabilities with a new Mobile Lab trailer and new control valve testing systems.     Finally, we continued our initiative to bring you valuable content related to valves, actuators, and the many industries we serve. Here are our top 5 industrial valve articles of 2016.     Maximizing Your Control Valve Performance: A Guide to Control Valve Selection, Maintenance, and Repair     Process plants can contain thousands of control valves, responsible for keeping process variables like flow, level, pressure, and temperature within the desired operating range. Despite their importance to product quality, efficiency, and a company’s bottom line, control valves are often neglected. This article provides an in-depth look at the factors that affect control valve performance and how to keep your valves always working their best.     It came to our attention earlier this year that some safety valves containing Thermodiscs (e.g., Consolidated 1811 and Consolidated 1711 series) were being put through hydrostatic testing. These valve parts are designed for steam service only and water can cause damage, potentially beyond repair. This article describes the problems that hydrostatic testing can cause and what you can do to mitigate these problems.     The American National Standards Institute (ANSI) and the International Society of Automation (ISA) provide standards for the hydrostatic testing of control valves. The goal of the test is to verify the valves’ structural integrity and leak tightness. This article summarizes the fluid, pressure, and time requirements of hydrostatic testing as well as the standards for acceptable performance.     To work properly when they’re needed, all valves must be maintained. It used to be that preventative maintenance was the only option. But with the diagnostic tools available today, it’s possible in some cases to use a data-based predictive approach instead. Both of these approaches are part of an effective valve disc maintenance program. This article helps you understand when each of them is most appropriate.     Sand casting can be used for the majority of metals. Even highly reactive magnesium is sand cast provided care is taken and the correct materials used by adding what are called inhibitors into the sand.     Sand castings inevitably have a slow cooling rate because of the large insulating mass of sand surrounding the liquid metal as it cools. Grain sizes and dendrite arm spacings tend to be larger than in equivalent section sizes in die-castings.     Sand casting involves the pouring of molten metal into a cavity-shaped sand mould where it solidifies (Fig. 6.8). The mould is made of sand particles held together with an inorganic binding agent. After the metal has cooled to room temperature, the sand mould is broken open to remove the casting. The main advantage of sand casting is the low cost of the mould, which is a large expense with permanent mould casting methods. The process is suitable for low-volume production of castings with intricate shapes, although it does not permit close tolerances and the mechanical properties of the casting are relatively low owing to the coarse grain structure as a result of slow cooling rate.     The goal of this experimental study is to manufacture a bolted GFRP forged flange connection for composite pipes with high strength and performance. A mould was designed and manufactured, which ensures the quality of the composite materials and controls its surface grade. Based on the ASME Boiler and Pressure Vessel Code, Section X, this GFRP flange was fabricated using biaxial glass fibre braid and polyester resin in a vacuum infusion process. In addition, many experiments were carried out using another mould made of glass to solve process-related issues. Moreover, an investigation was conducted to compare the drilling of the GFRP flange using two types of tools; an Erbauer diamond tile drill bit and a Brad & Spur K10 drill. Six GFRP flanges were manufactured to reach the final product with acceptable quality and performance. The flange was adhesively bonded to a composite pipe after chamfering the end of the pipe. Another type of commercially-available composite flange was used to close the other end of the pipe. Finally, blind flanges were used to close both ends, making the pressure vessel that will be tested under the range of the bolt load and internal pressure.     In manufacturing of the steel bridge, fillet welded T-joint is widely used and angular distortion is often generated. So, reduction or control of angular distortion without additional processes to welding is strongly demanded because it takes great time and effort to correct the angular distortion. In this study, the effectiveness of welding with trailing reverse-side flame line heating for preventing angular distortion was investigated through the welding experiment and numerical simulation in submerged arc welding of fillet T-joint with three different thick flange plate. First, the heat source models for numerical analysis of both submerged arc welding and flame line heating were constructed based on the comparison with the measured temperature histories and angular distortion. And then, these heat source models were used in combination with various kinds of distance between two heat sources to make clear the appropriate distance condition for smallest angular distortion was 150 mm, and it does not depend on thickness of flange plate. It was also confirmed that the experimental angular distortions were in good agreement with those calculated. With a focus on the influence of thickness of flange plate, the reduction of angular distortion by welding with trailing reverse-side flame line heating becomes smaller with increasing thickness of flange plate. However, angular distortion could be adequately prevented under the appropriate flame line heating condition in either thickness of flange plate because the welding-induced angular distortion also becomes smaller with increasing thickness of flange plate. Thus, it was concluded that welding with trailing reverse-side flame line heating could be useful for preventing angular distortion of fillet T-joint, which is a component of steel bridge, enough not to correct it after welding.     Garlock offers a range of Butterfly Valves for different applications. Ranging from GAR-SEAL Butterfly Valves are used extensively where corrosive, abrasive and toxic media, to STERILE-SEAL valves are used in applications where sterile processes need to be maintained in the pharmaceutical and food industries.     Depending on your application, different air valve material and design type should be used. For a better understanding on which type of Garlock Butterfly Valve will best fit the application, you can refer to our Chart     The mechanism of opening of the aortic valve was investigated in dogs by attaching radiopaque markers to the commissures and the leaflets. Analysis of abnormal cardiac cycles demonstrated that, when the ventricular pressure first equalled the aortic pressure, the intercommissural distances increased 9 percent, and the valve opened with a stellate orifice without forward flow and without a rise in aortic pressure. Further opening of the aortic valve was dependent on forward flow over a narrow range. A new mechanism of aortic valve opening is proposed. This mechanism results in minimal flexion stresses on the leaflets and is important for the longevity of the normal aortic valve. It can occur only if the leaflets arise from an expansile aortic root.     Original LESER spare parts are the guarantee that also after maintenance works your safety valve precisely fulfills its task to protect people and environment. Learn with the spare pare finder which subassemblies are installed in your individual safety valve to be able to order the correct LESER spare part. The spare part finder shows the bill of materials of your individually configured valve body.     The list shown contains all components, regardless whether they are needed as spare parts. As initial spare parts supply for API, High Efficiency, High Performance, Compact Performance and Modulate Action safety relief valves, we recommend the Spare Part Kits. For the other product groups please contact us for an inital spare part offer. Find out more about LESER-Spare Parts Kits.     Please enter a combination of a serial number (SerNr.) and an article number (ArtNr.) to bring up the right spare parts (e.g. SerNr: 10202021, ArtNr: 4411.4443). You can find the serial and article numbers on the name plate of the valve or on the Certificate for Gobal Application, which you can download in the CERTIFICATES-area.     Please pay attention to the following user instruction:     The spare part finder currently only shows bills of materials for valves assembled in our Hohenwestedt plant. For spare parts lists of other valves, please contact your local partner.     Some items in the bill of materials are subassemblies which contain one or several of the following items. In most cases the subassembly should be ordered as a spare part.

Publish Date: 2021/08/19

Ultimate flexibility for scalable aseptic filling

Description:     Ultimate flexibility for scalable aseptic filling     For more than 30 years, Flexicon has been established as the preferred choice for aseptic liquid filling for GMP regulated industries, such as biotechnology and diagnostics     Flexicon’s products scale with your business. From the intuitive, easy-to-use design of our ergonomic pumpheads, through to the modular design of manual, semi and automatic systems, our products feature a grow-with-me concept to meet your fill/finish needs.     Our experience in engineering accurate and reliable bottle filling machine for sensitive fluids in GMP production and cleanroom environments, means we provide solutions to optimise your fill/finish processes.     As part of the Watson-Marlow Fluid Technology Group, Flexicon’s engineering is backed by a global network of specialist and technical support engineers, who can help optimise your complete development and filling process, wherever you are in the world.     At the heart of all our filling systems is the gentle pumping action of our peristaltic fillers, which ensure your valuable product is transferred without cross contamination or damage to viability and product quality.     Leveraging our expertise in peristaltic engineering has helped to optimise the performance of companies filling processes worldwide. Whether those companies are developing Advanced Therapy Medical Products (ATMP) or looking to quickly—and safely—scale-up their batch production, we can help develop a system tailored to your needs.     Whether you’re a newcomer to the world of liquid filling equipment or an experienced user looking to upgrade or change your production line, browsing websites and product catalogues in the search to source a suitable machine can be more than a little confusing.     Overflow or gravity machine? Piston or pump? Automatic, semi-automatic or manual? Hot or cold-filling? In-line or rotary filling? Off-the-shelf or turnkey? Fortunately, with so many choices out there you’re likely to find the ideal solution for your particular application – however, finding it requires that you do a bit of homework and adopt a systematic approach.     To simplify the process, you may find this guide to liquid filling equipment useful. It identifies key questions which will help you narrow down your search and focus only on those systems that meet your objectives.     The first question to ask is what product is being filled?     Not all liquids are the same. Some are free-flowing, others are very viscous. Some contain particulates or flammable ingredients, others are foamy whilst the viscosity of some products may change when the temperature changes. The important thing to remember is that type of liquid filling equipment that you choose has to be compatible with the product type. For example, a gravity filler is more suitable for thin products, piston fillers are a better option for thick products than overflow automatic liquid filling machine and bottom-up filling machines are used for foamy products.     Another key question to ask is what type of container is being filled?     In many instances, the type of container or bottle will dictate the type of filling technique and the more you know about the attributes of the container, the better. What material is it made from (e.g. glass, aluminium, plastic) and what are its dimensions and characteristics? This information is important because it will determine the optimum performance of the equipment and the best equipment type. For example, an automatic bottle filler which grabs a container from the side may not actually be the best option if your container is very wide and a top filler may not work if your container has an unusually-shaped cap or lid.     You need to ask how many containers do you want to fill every hour?     Knowing your production rate is also a crucial factor in your equipment selection.     A semi-automatic filling machine would be a cost-effective and reliable solution for smaller production runs like those in a laboratory or in a start-up venture, whilst an automatic filling machine with a sizeable conveyor is ideal for larger-scale operations with much higher production rates. For operations with very low production rates and no expansion plans such as a home brewing venture or small-scale home-made sauce business, a manual machine could fit the bill.     You also need to ask yourself, how do you want the final fill-level in your container or bottles to look?     Appearance does count, and different filling systems have different outcomes. For example, a liquid level machine will fill every container to the same specified level regardless of the volume of the product, making it a preferred product where uniformity is important. On the other hand, a volumetric filler will fill a container with the identical volume of liquid even when the fill levels may appear to be variable. Volumetric fillers generally cost more as they require specialized instruments for calibration, balance and timing.     Some of the types of liquid filling machines include:     gravity fed fillers (a good, cost-effective option for efficient volumetric filling especially for low viscosity and foamy liquids);     piston fillers which use a highly accurate volumetric filling technique, ideal for thick or highly viscous liquids. These are divided into two types, namely check-valve piston fillers and rotary valve piston fillers;     pump fillers which are very versatile and suitable for a wide range of liquids and viscosities     in-line filling machines (a cost-effective choice for filling containers in a line) which are suitable for those operations where different container sizes are involved; and     rotary filling machines (which are often much larger and more specialized) for faster speeds and higher production rates.     Another question is whether your filling equipment can be modified if your needs change?     It’s often not necessary to buy new equipment just because your business has expanded or you want to add new products or packaging to your line. An experienced manufacturer will have the knowledge and skills to advise whether your liquid filling system can be modified and will make recommendations to future-proof your investment.     Choosing the best liquid filling equipment is a complex decision and many factors need to be considered.  From product characteristics and container attributes to fill size, production rates, regulatory issues, safety requirements and expansion plans, if you answer the questions highlighted above, you’ll be in a strong position to make an informed choice which factors in all of these issues.     However, your best option is to talk directly to industry professionals, like AccuPak. They are one of Australia’s largest suppliers of all types of packing and filling equipment and they will work with you to identify the most cost-effective and practical solution. They know the critical factors required from all packing, filling, bagging and palletizing machinery and equipment - i.e. versatility, flexibility, reliability, accuracy and affordability - and if you’re interested in finding out how they can help you achieve your objectives, get in touch with them on 03 8804 1529 or visit accupak.com.au.     A walk down the grocery store aisle will exemplify the overwhelming amount of beverage products to choose from these days. Even with the existing wide variety of flavors and concepts within each drink category, consumers seem to want even more. For example, one of the fastest-growing segments in the beverage industry continues to be craft beer. Even after the beginning of its meteoric rise a few years back, the number of specialty beers with unique ingredients and different styles continues to proliferate with other craft alcohol producers, such as cider and spirits, following close behind. To keep up, many facilities are designing and installing additional liquid filling lines.     “As product lines continue to evolve to match expanding consumer demands, manufacturers are seeking flexible equipment that allows for product modifications—without breaking the bank,” says Paul Grainger, technical key account direct or North America for Tetra Pak. “Today’s equipment simply must be designed to accommodate a diverse range of products in order to be viable.”     Additionally, to maximize production efficiency, many are turning to high-capacity and more automated equipment that provides this flexibility. Still top of mind, though, are accuracy, minimizing product waste, reducing changeover times and simplifying sanitation. Liquid filling equipment providers are working to meet all these needs and more.When picking a specific 5 litre liquid filling machine, a good place to start is to know the exact characteristics of the liquid product. Is it a free-flowing liquid? This might work better with a timed-flow fill machine where the same volume of product is delivered each cycle. What if the product is more viscous? For that, a positive displacement liquid filler might be the way to go.     “Product specification is the most important parameter that we, at Bosch Packaging Technology, need in order to identify a suitable piece of filling equipment for our customers,” says Jonathan Viens, manager of North American sales and marketing. “We are talking about product characteristics, such as filling temperature, particulates, tendency of the product to splash or froth, etc.”     He explains that if a company is trying to dispense baby food into containers, Bosch would suggest servo-driven aseptic1 litre filling machine with full-metal pistons. This type of equipment helps address precision in filling a product that is highly viscous and particulate rich, but also avoids weight fluctuations or overfill issues.     For products that need special attention paid to minimizing microorganisms and ensuring food safety, such as juices, hot-fill technology for hygienic bottles will be needed. This was the case when Coca-Cola Canners in South Africa started bottling iced tea, sports drinks and juices with and without fruit chunks. The facility had two existing PET bottling lines, but due to the high-pulp content of the juice, a new line was needed.     The company employed KHS, a manufacturer of filling and packaging equipment, to install a hot-fill line. The content is heated to over 100°C and filled at a temperature of approximately 83°C. The line can fill up to 48,000 bottles per hour, sized between 0.3 and 1.5 liters. To avoid damaging the fruit chunks during the filling, the line was equipped with two precision volumetric fillers where the fruit pieces are first bottled with a small amount of juice before the second filler tops off the bottles with pure juice. This understanding of the filler’s impact on the final product is important, especially for sensitive liquids.     “Some yogurts tend to ‘shear’ when being forced through small openings,” says Jan Sundberg, applications development manager for JBT Corporation. “The filler needs to have gentle handling inside the filler bowl/hopper and also as the product flows through the valve. Larger porting and short, straight paths for the product flow are key to minimizing any damage.” For instance, features like extra elbows, pipes and pumps can change the viscosity of a product, so eliminating them for these applications could offer protection against damage.     “Products like creams or oily dressings can only be dosed with a specific dosing station, for example, positive valve,” says Viens. “Otherwise, the rotary movement in standard dosing stations could damage the product, or the pump design could separate the oil from the base product.”     When bottling a product like beer, which has a tendency to foam, gentle filling is paramount. Breweries want to limit the amount of oxygen picked up by the beer as much as possible during the filling process, but also want to maximize throughput. To help address these issues, Krones has equipped its Modulfill filler with a level probe that includes a swirl.     “The swirl gently guides the liquid to the bottle wall and in the bottle,” says Stefan Kraus, product manager for filling technology. “Additionally, the filling valve is equipped with two different filling speeds. The result is a gentle filling process with low turbulence and less foaming behavior.”     Product and container versatility     Because of the wide variety of products being packaged at plants, more processors are looking for fillers that can handle multiple concepts. Equipment providers understand this, but might not be able to deliver a panacea yet.     “In the world of food, the day of ‘one filler fits all’ still hasn’t arrived due to the wide range of product characteristics,” says Viens with Bosch, which acquired filling and sealing equipment manufacturer Osgood Industries, Inc. in 2015. When Bosch Osgood introduced its tank-style pump, part of the objective was to address this need for fillers to handle many different types of products. Thus, the tank-style pump can handle a range of products, from liquid juice to viscous vat-set yogurt. “With this solution, the pistons that are used to pump the product are located inside the hopper. An even distribution of product above each piston and tight tolerances offer the user excellent lane-to-lane repeatability and eliminate the need for dynamic O-rings on the piston head.”     “Customers are demanding that new filling equipment is more versatile and can handle a full range of varying products,” says Sundberg. As a result, the JBT Unifiller filler can handle products with a thin, watery consistency to thick, chunky products with high solid content and large particulates. “ is a unique volumetric piston filler with short product paths and larger porting.” Additionally, the fill nozzles are designed for specific applications and can be easily exchanged.     Krones 6 head liquid filling machine are also designed with flexibility in mind, says Kraus. As an example, he cites some of the company’s filling equipment that can be adjusted automatically via the filling probe, which addresses improved automatization as well.     For most of its filling machines, Serac uses net weight filling technology, which controls the amount of product dispensed into the container to give an accurate measure of what is inside. Alan Bonanno, marketing manager for Serac, says because aeration, temperature and viscosity do not affect the accuracy of a net weight filler, it can handle a variety of products with different characteristics.     Product flexibility isn’t the only filling demand, but the shapes, sizes and materials used in different containers being filled are also highly variable. Knowing the type of container is important for packaging providers to understand, says Viens, as it “will drive the configuration on numerous machine stations and the number of lanes required.”    

Publish Date: 2021/08/19

The science behind wet wipes for infant skin

Description:     The science behind wet wipes for infant skin     In the diapered area, the continuous exposure to excess moisture and irritants from urine and feces weakens the stratum corneum, making the skin more susceptible to irritation. The use of wet wipes for infants (baby wipes) is a common practice to clean skin after urine or a bowel movement, and this practice even extends to cleaning the hands and face, resulting in repeated daily use. Therefore, ensuring that baby wipes contain ingredients that are safe and mild on skin is important to help minimize skin irritation and discomfort. While disposable baby wipes have been shown to be effective and gentle at cleaning infant skin, even the skin of premature infants, there is growing public concern regarding their safety and tolerability. Not all products are made the same, as differences exist in manufacturing processes, ingredients, materials, safety, and quality testing. Therefore, it is important that healthcare professionals have accessible evidenced-based information on the safety and tolerability of common ingredients found in baby wipes to optimally educate their patients and families. Herein, we provide a review on best practices for ingredient selection, safety, and efficacy of baby wipes.     Skin irritation in the diapered region (commonly referred as diaper dermatitis) is one of the most common skin disorders found in infancy, with the highest incidence at 9-12 months of age.1 Overhydration and prolonged exposure to urine and feces are known to be the main contributors to skin irritation in the diapered area.2 However, an infant's diet, medications, underlying skin conditions, certain product ingredients, caretaker behavior, and practices such as infrequent diaper changes or ineffective cleaning can also influence the occurrence of diaper dermatitis. It has been reported that the diapering process can be a stressful event for an infant.3 The presence of skin irritation can exacerbate this response, leading to increased pain and discomfort. Ensuring the diapered area is kept dry and clean and that products used do not adversely impact the skin can help minimize the occurrence of dermatitis in the diapered region and, in turn, provide comfort to the infant.     Herein, we provide a review on best practices for ingredients selection, safety, and efficacy of runhe baby soft wet wipes to help make more informed decisions when selecting products for infant diapered skin care.     A disposable baby wipe consists of three main components—the basesheet (the cloth that makes the wipe), the formulation (the ingredients in the solution that make the wipe wet and help with cleaning), and package, as shown in Figure 1. The packaging (not discussed here) and the basesheet are the most physically obvious components of a wipe. There are three types of basesheets with differences in composition which translates into differences in thickness, absorbency, and softness to touch. These differences can impact cleaning performance but the materials themselves are quite common—wood pulp, polypropylene, polyester, or combinations thereof.     Over the last two decades, significant advances have been made to baby wipes. More recently, efforts have been centered on the removal of ingredients with irritation or skin-sensitizing potential such as methylisothiazolinone (MI) and phenoxyethanol.4 In fact, five clinical studies have demonstrated that the use of modern baby wipes is superior to using water and cloth to clean diapered skin (see Table 1). In 2016, a recommendation was made by the European Roundtable Meeting on Best Practice Healthy Infant Skin Care stating that a wet wipe for infant skin should contain pH buffers to maintain the slightly acidic pH of the skin, should be free of potential irritants, and should contain well-tolerated preservatives     Formulating a hypoallergenic, safe, gentle, and effective baby wipe can be challenging as the wipe must meet regulatory, safety, and performance measures while remaining aesthetically pleasing. It is preferred that baby wipes are formulated with a very large percentage of water. However, water alone is not enough to effectively remove water-insoluble residues from feces and prevent the growth of microorganisms or maintain a healthy skin pH. Thus, it is important that baby wipes also contain an extremely mild surfactant (detergent or cleanser) to lower surface tension for better cleaning, a preservation system to ensure product freshness before and during use, a pH adjusting (buffering) system to maintain a solution pH similar to infant skin, and, optionally, skin-benefiting ingredients that reduce frictional damage, replenish the skin lipids, etc A common misconception about baby wipes is that they contain drying alcohols such as ethanol and isopropanol. While ethanol and isopropanol can be found in some sanitizing wipes, these ingredients have not been used in branded baby wipes.     The water used in baby wipes should range from highly purified to reverse osmosis quality. The treatment process removes most of the salt content (CaCO3 and MgCO3, contributing to overall hardness) and other residual minerals that can serve as nutrients for microorganisms. Most water systems also employ ozone and ultraviolet light processing to sterilize the water before use. In addition, extensive filtration removes total dissolved solids and microbes. These intentional processes produce water that is of a higher quality than standard drinking water and some types of distilled water.     2.2.2 Surfactants     Surfactants are the molecules within the formulation that provide cleaning action. Surfactants contain hydrophilic moieties attached to hydrophobic end chains. It is the hydrophobic end chains that bind to oily residue on the skin surface and help remove it. For baby wipes, it is important to use a surfactant that can adequately remove the oily molecules within feces without removing skin lipids, which can lead to skin barrier damage with repeated or prolonged use. For runhe new arrival baby wipes, the surfactant fraction would not be expected to exceed 1% by weight of the formula and, in most cases, would be below 0.3% by weight.6 This is in stark contrast to bottled baby products (body wash, shampoo, hand soap) where the surfactant concentration is typically between 5% and 20% by weight as dilution is expected upon use followed by rinsing.6     Surfactants are typically classified as anionic (negatively charged), cationic (positively charged), and non-ionic (no net charge). Generally, non-ionic surfactants are the mildest on skin; however, there are examples of suitable surfactants in all classifications. Table 2 contains a list of typical baby wipe surfactants along with maximum use concentrations and references to full reviews on their safety profile as concluded by the Cosmetic Ingredient Review (CIR), an independent expert panel consisting of dermatologists, toxicologists, academic researchers in medicinal and pharmaceutical sciences, industrial scientists, and representatives from the FDA and consumer groups.     As baby wipes contain a large amount of water, this can allow microorganism growth. To prevent contamination, various manufacturing and testing practices are followed by major suppliers. The use of preservatives ensures the product is not contaminated before the consumer begins using it, and that it maintains a reasonable shelf life for use. Ensuring a consistent product, free of pathogenic microorganisms, should be of the highest concern, especially when cleaning infants with compromised skin.     In the personal care industry, the default listing of preservative chemicals is maintained by the European Union (EU) and is known as Annex V.7 Ingredients on this list are recognized for their antimicrobial action and listed with acceptable and safe usage concentrations. A subset of these chemicals applicable to baby wipes is shown in Table 3. Notably, many of the chemicals in Annex V are not allowed for use in children's products due to regulation at the state or country level. The US FDA does not maintain a list of approved preservatives but does have the authority to limit the use of ingredients in certain product classifications. After considering safety, allergenicity and irritation potential, the choice of preservative in a formulation depends on water solubility, effective concentration, pH compatibility, odor, and consumer expectation. A good example of regulatory and industrial response has been the removal of formaldehyde donating preservatives and MI from wipes and other leave-on products following many reports of contact dermatitis and sensitization in the diapered area and in other common areas of baby wipes use such as hands and face. Currently, it is rare to find this ingredient in mainstream baby soft wet wipes.     A critical part of ensuring baby wipes are safe and effective to clean infant skin is following specific microbiological quality standards prior to product distribution. As is the case with most non-sterile formulated personal care products, baby wipes require specific analyses to ensure they (1) do not contain harmful or high levels of microbes following manufacturing and (2) can control the growth of microbes introduced during use. Non-profit scientific organizations, such as the United States Pharmacopeia (USP) and the European Pharmacopeia (EP), have published guidelines on the preferred approaches for completing these analyses.     Prior to releasing baby wipes for sale to consumers, an evaluation of the final product should be completed for the presence and level of microbes within the product. For example, the USP recommends that methods used in the release of non-sterile products have data available that demonstrates the ability for methods to successfully recover and quantify Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus brasiliensis.21     Any products that have a water activity level of >0.90 are susceptible to the growth of microbes in the product as this is the minimum level of water required for bacteria and fungi to grow.22-24 As such, products at or exceeding this level of water, such as wipes, should include a preservative to prevent the growth of microbes that may be introduced post-manufacturing. A likely route of post-manufacturing product contamination is while dispensing the product during use,25 a reason why packaging is a key component. In this scenario, transient or normal flora from a wipes’ user can transfer from the hands onto the stack of wipes in the product package. To assure a newborn baby wipes product is effectively preserved and able to overcome this type of contamination, a confirmatory lab test must be utilized to ensure microbial growth will not occur during normal product use. Specifically, the test should involve adding a defined number of diverse organisms (at a minimum those recommended by USP/EP but others may be added) to a defined quantity of product and then monitoring the survival and/or growth of the added organisms over time.26 This test is commonly utilized on product that has been freshly made and on product aged under ambient or accelerated (high temperature, high relative humidity) conditions. While there is no universally applied approach in how this test is conducted for wipes, many manufacturers utilize USP and/or EP guidance as the basis for establishing their method and acceptance criteria.     The performance of the preservative system is one of the most important factors that go into determining the expiration date on the package. Baby wipes that do not have a proper preservative system should have a much shorter expiration date (or period after opening) as the product does not have a means to prevent microbial growth post-manufacturing. This is especially critical when the dispensing of the wipes requires significant contact by human hands, that is, transfer of normal flora into the package. Wipes should not be used outside of the printed expiration dating on the package and should be stored as directed by the labeling on the package.

Publish Date: 2021/08/19

Knit fabrics are constructed by interloping one or more sets of yarns

Description:     Knit fabrics are constructed by interloping one or more sets of yarns     Common examples of apparel utilizing weft knitted fabric are socks. Knitting is a more versatile manufacturing process, as entire garments can be manufactured on a single knitting machine, and it is much faster than weaving. However, due to the looping, more yarn is required to manufacture a knitted garment than a comparable woven garment. Thus any cost savings gained in manufacturing speed are offset by the higher materials cost.     Knits are comfortable fabrics, as they adapt to body movement. The loop structure contributes to elasticity beyond what is capable of the yarns or fibers alone. A knit fabric is prone to snagging, and has a higher potential shrinkage than a woven fabric. The loop structure also provides many cells to trap air, and thus provides good insulation in still air. Knits are not typically very wind- or water-repellent.     Knit fabrics are composed of intermeshing loops of yarns. There are two major types of knits: weft knits and warp knits, as illustrated in Fig. 4.7. In weft knits, each weft yarn lies more or less at right angles to the direction in which the fabric is produced, and the intermeshing yarn traverses the fabric crosswise. In warp knits, each warp yarn is more or less in line with the direction in which the fabric is produced, and the intermeshing yarn traverses the fabric lengthwise. Similar to the way that woven fabrics have warps and wefts, knit fabrics have courses and wales, which lie in the crosswise and lengthwise direction, respectively. However, unlike woven fabrics, courses and wales are not composed of different sets of yarns; rather are formed by a single yarn.     Weft blend knitted fabrics are produced predominantly on circular knitting machines. The simplest of the two major weft knitting machines is a jersey machine. Generally, the terms circular knit and plain knit refer to jersey goods. The loops are formed by knitting needles and the jersey machine has one set of needles. Typical fabrics are hosiery, T-shirts, and sweaters.     Rib knitting machines have a second set of needles at approximately right angles to the set found in a jersey machine. They are used for the production of double-knit fabrics. In weft knits, design effects can be produced by altering needle movements to form tuck and miss stitches for texture and color patterns, respectively. Instead of a single yarn, several yarns can be used in the production of these structures. This increases the design possibilities.     ‘Loop’ is the basic unit of knit fabric. As illustrated in Fig, 4.7a, in weft knits, a loop, called a needle loop, consists of a head and two legs, and the section of yarn connecting two adjacent needle loops is called the sinker. In warp knits, the needle loop is divided into overlap and underlap, as illustrated in Fig. 4.7b. Each loop in a printed fabric is a stitch. Alternative to fabric count for woven fabrics, cut (or gauge) and stitch density are used to represent the closeness of the intermeshing loops. Cut or gauge indicates the number of knitting needles per unit length along the crosswise or lengthwise direction. The greater the number, the closer together the loops are to each other. Stitch density is the number of stitches per unit area, obtained by multiplying the number of courses per inch (25 mm) by the number of wales per inch (25 mm). Like woven fabrics, a knit fabric also has a technical face and a technical back and can differ in appearance on each side. The technical face is the side where the loops are pulled toward the viewer. Knit fabric also has an effect side, which is intended to be used outermost on a garment or other textile product. In some cases, the technical face and the effect side are the same; but in others, they are opposite.     Gel Knit? fabric is a small diameter weft knitted tube. This is knitted on a small diameter circular knitting machine with the provision for the positive feeding of two separate yarns. Positive feeding is used to ensure the good quality assurance required for a medical product.     The main yarn that is knitted is a staple (spun) yarn of cellulose. This may be any normal cellulosic textile material such as cotton or a number of different reconstituted cellulose materials such as lyocel or viscose. As will be described later in this paper, the cellulose is the precursor material since it will be chemically converted after knitting into the Gel forming material.     The second yarn is a very thin continuous filament nylon which acts as reinforcement and holds the fabric together after the Gel has been formed and the Gel forming yarn has lost all form and stability. The total nylon content of the fabric is about 10%.     Warp knit fabric is similar to that of a woven fabric in that yarns are supplied from warp beams. The fabric is produced, however, by intermeshing loops in the knitting elements rather than interlacing warps and wefts as in a weaving machine. Warp knitted fabric is knitted at a constant continuous width. This is achieved by supplying each needle with a yarn (or yarns) and all needles knit at the same time, producing a complete course (row) at once. It is also possible to knit a large number of narrow width fabrics within a needle bed width to be separated after finishing. In comparison with weft-knit structures, warp knits are typically run-resistant and are closer, flatter and less elastic.     The two common warp-knit fabrics are tricot and raschel (Fig. 10.9). Tricot, solely composed of knit stitches, represents the largest quantity of warp knit. It is characterized by fine, vertical wales on the surface and crosswise ribs on the back. Tricot fabrics may be plain, loop-raised or corded, ribbed, cropped velour or patterned designs. It is commonly used for lingerie owing to its good drapability. It is used for underwear, night-wear, dresses, blouses and outerwear.4 Tricot fabric is used in household products such as sheets and pillowcases. It is also be used for upholstery fabrics for car interiors.Most warp cotton stripe jersey knit fabrics tend to curl, including the most important type known as Jersey stitch (in the USA) or Locknit stitch (in the UK). If they receive appropriate heat treatment, synthetic warp knit fabrics do not curl. In dyeing, finishing, cutting and sewing garments, it helps to know the face and back of the fabric and its curling propensity. When a greige nylon Jersey stitch fabric is put on a table technically upright (having the loop side up), the top and bottom edges of the fabric will curl upwards or towards the loop side or technical face. However, the side edges will curl under the fabric towards the float or technical backside of the fabric.     If nylon Jersey stitch fabric is heat set it will not curl, but if that fabric is laid on the table technically upright and it is pulled sideways on the top edge of the fabric, the fabric will curl towards the loop side. There are some warp knit structures that will not curl in the greige state.Plain warp-and weft-knitted structures are not commonly used for composite applications due to their inherent anisotropy in the wale and course directions. This causes the fabric preform to roll up on itself making handling and manufacturing more difficult. This problem is solved by using weft-knit structures such as the 1 × 1 rib and milano rib, which exhibit balanced properties because of their through-thickness symmetry. However, the highly curved fibre architecture, or crimp, present in these and any knitted structure, means that composites produced using these structures exhibit relatively poor mechanical performance. Characteristics of high conformability and low strength make them ideally suited to producing semi-structural complexly shaped components.     To help increase mechanical performance, insert yarns can be placed between the planes of loops in either the warp or weft direction. The technique can be used for both warp-and weft-knitted fabrics which allow the insert yarns to remain perfectly straight, giving a greater yarn to fabric translational strength. This results in an increase in the composite stiffness and strength along the insert direction. Warp-and weft-knitted fabrics with inlay yarns are termed unidirectional knitted fabrics and the incorporation of insert yarns in two directions creates biaxial knitted fabrics.     8.4.1 Multiaxial warp knits     Multiaxial Warp Knit (MWK) fabric is a further development of this idea by utilising layers of insertion yarns for the in-plane reinforcement and warp stitch yarns for the through-thickness reinforcement. They consist of one or more parallel layers of yarns held together by a warp knit loop system. Theoretically, as many layers as preferred can be used but typical commercially available machines only allow four layers (Du and Ko, 1996). The purpose of the knit loops is to hold the layers of unidirectional yarns together, but it has also been proven to be the key to increasing the damage tolerance of the material (Zhou et al., 2005).     These types of knitted structure are termed non-crimp structures and can be produced in a single knitting process (Du and Ko, 1996). They are particularly suitable for thin to medium thickness parts. The combination of the warp-knitted structure and non-crimp yarns means they have the ability to conform to complex shapes as well as the potential to meet the demands of primary load bearing applications.     MWKs have evolved through structural modifications of warp-knitted fabrics and are predominantly fabrics with inlay yarns in the warp (90°), wale (0°) and bias (± θ°) directions. Warp, weft and bias yarns are held together by a chain or tricot stitch through the thickness of the fabric (Du and Ko, 1996). Layers of 0° need to be placed somewhere other than the top or bottom layer to ensure structural integrity. The amount of fibre and the orientation of the inlay yarns can be controlled, which is advantageous for preform engineering. As a result, the insert yarns are made from a much higher linear density yarn than the stitch yarns, since they form the load-bearing component of the fleece fabric structure (Du and Ko, 1996). Figure 8.4 shows the configuration of the chain and tricot MWK structures.Yarns in a simple weft-knitted structure, as shown in Figure 11.13a, lack the long continuous paths found in woven fabrics and there would be stress concentrations where yarns cross one another. This limits their mechanical performance, but as shown in Chapter 3, they do have applications as composites. In the free state, the knit fabric shows a low resistance to extension and shear, with accompanying area change, until the yarns jam together. This means that they are easily draped into complex shapes.

Publish Date: 2021/08/19

Abrasive Material

Description:     Abrasive Material     Blasting is carried out with abrasive materials such as chilled iron grit, steel or aluminium oxide grit. Sand or other substances containing free silica must not be used, as anyone exposed to dust from it could develop silicosis.76     In a factory, blasting operations should be carried out in a suitable enclosure or room to protect other personnel from injury and nearby machinery from damage. The ‘blast room’ should be provided with an efficient system of exhaust ventilation, preferably of the down-draught type. During the blasting operation super abrasive material rebounds from the surface of the article with a high velocity. Consequently the operator must be given special protective clothing such as gloves, apron and leggings. A helmet supplied with fresh air at a positive pressure is also necessary to protect the blaster from both flying particles and harmful dust.82     Because of the friction between the finely divided particles of grit and the blasting hose and nozzle, discharges of static electricity occasionally take place. It is advisable to earth the blasting hose and nozzle.     The sand blasting technique is based on blasting an abrasive material in granular, powdered or other form through a nozzle at very high speed and pressure onto specific areas of the garment surface to give the desired abraded look. A straighter surface and less effect can be obtained with the sand blasting process than with the sanding process, and sand blasting can be done in less time. For this reason, it is more advantageous in terms of costs. However, silicon grains that are located in the sand can cause silicosis disease. The sand blasting process is now prohibited in most countries because of its negative effect on human health (Suglobal Tekstil, 2013; Paul and Naik, 1997a; Paul and Pardeshi, 2003).     Very hard surfaces can be studied by the abrasion of the surface with a sheet of abrasive material, such as silicon carbide or carborundum paper. At this point a number of different methods may be used to analyze the abraded material. In essence, any solid sampling technique that is capable of handling fine powders—KBr pellet, diffuse reflectance, ATR, photoacoustic, etc.—may be used to study the material. An interesting variant is to use diffuse reflectance to study the abrasive (see the reference to the silicon carbide method in Section 4) for the residual material.     Materials used as abrasives include both natural minerals and synthetic products. Abrasive materials can be considered as cutting tools with geometrically unspecified cutting edges that are characterized by high hardness, sharp edges, and good cutting ability. The sharpness of abrasive grains may be described in terms of edge radius and apex angle. As grain size increases, the percentage of sharp apex angles decreases, indicating a deterioration of grain cutting ability. In addition, cutting ability depends on specific features such as grain structure and cleavage, which are connected with the ability of cutting grains to regenerate new sharp cutting edges and points.     The choice of abrasive for a particular application may be based on durability tests involving impact strength, fatigue compression strength, dynamic friability, and resistance to spalling which occurs under the influence of single or cyclic thermal stress.     The abrasives industry is largely based on five abrasive materials; three are considered to be conventional abrasives, namely silicon carbide (SiC), aluminum oxide (alumina, Al2O3), and garnet. The other two, namely diamond and cubic boron nitride (CBN), are termed superabrasives.     A primary requirement of a good abrasive flow is that it should be very hard; but hardness is not the only requirement of an abrasive. The requirements of a good abrasive are discussed below. The decision to employ a particular abrasive will be based on various criteria relating to workpiece material, specified geometry, and removal conditions.     Cutting fluids should be used wherever possible in grinding to achieve high material removal rates coupled with low wear of the grinding wheel.     Mechanical polishing is done on a rotating disk covered with a felt, and is sprayed with a very fine abrasive materials (e.g., aluminum oxide or magnesium oxide). Because of, not creating grooves on the samples, brush or the felt that is employed here, should be thick and have no hard particles especially dust. At the entire period of polishing, it is necessary to smear the felt with suspended aluminum dust in water frequently. Grading of the aluminum oxide particles is different and we usually polish hard materials such as steel and cast iron with coarser aluminum powder rather than the soft metals like aluminum and lead. The alumina is in two forms: allotropic alpha (hexagonal) and gamma (cubic). The polishing properties of these two forms are different, so that alpha alumina acts faster in abrasion of metals and is more suitable for rough polishing, while gamma alumina prepares a polished surface with the high quality, so it is apt for the final polishing. Sometimes, it is utilized magnesium oxide for polishing aluminum and its alloys. This substance absorbs the carbonic gas of the air and produces carbonate. Therefore, aluminum oxide is usually used in the metallurgy laboratory. A disk with a velvet coating and diamond powder is being used to obtain a mostly polished surface and devoid of any grooves. Often, it is better to use an appropriate lubricant such as alcohol for synthetic diamond paste, to remaining free or rising up the power of cutting powder of diamond particles, and also to increase the life of velvet coating.     In our day-to-day life, few manufactured products in their production process escape a finishing and/or grinding operation involving abrasive materials. Whatever their origin, abrasive minerals or abrasive tools, their economic weight is huge; more than 10 B€ for the overall abrasives and around 2B€ for the abrasives minerals markets. The other way to assess the importance of such products is the number of patents published regularly; more than 50,000 per decade since the year 2000 (Nadolny, 2014). However, these patents are firstly, mainly related to abrasive tools and secondly, focused on super abrasives – around 10,000 patents per decade these last decades – as well as microcrystalline abrasive materials using sintered abrasive ceramic grains.     For scientists the difficulty will be to evaluate what will be the final performance of their abrasives grains in the numerous end user applications, knowing that such performance is a 50/50 combination between the abrasive grain and the abrasive tool; a common approach in the industrial abrasives community.     Although abrasive minerals are never studied from a detailed academic point of view, for industrial scientists there are big challenges which require scientific knowledge across a broad range of materials science such as crystallography, high temperature chemistry, surface chemistry, tribology, technical and advanced ceramic processing etc. This is what will be seen in the following part of this chapter which is based upon industrial experience of the author.Powder blasting is not selective in terms of chemistry; hence, it will etch any material with similar elastic properties at the same rate. Unlike chemical etching (which is chemically selective), powder blasting will continue to etch through substrate materials if the mechanical properties are comparable to those of the film. For example, a silicon substrate will continue to be etched once the ceramic film has been patterned. Due to the high etch rates, it is often not possible to prevent the underlying substrate from being attacked. It is also important to note that thin layers of ductile material will not resist removal if the underlying material is brittle, as any particle impacts will cause the underlying material to fracture, thereby lifting the thin metal film off. This can be seen where thin metallic electrode layers (100–200 nm) are removed when etching through a ceramic film.     It is possible to achieve a degree of selectivity by choosing the appropriate blasting media. The rate of material removal is a function of the difference in hardness between the blasting media and the target material, as well as the kinetic energy of the blasting media. Very hard blasting media with high kinetic energy (i.e. large mass and high speed) will exhibit high removal rates. For example, very hard blasting material such as alumina will remove the majority of materials, while softer materials, such as cornstarch, show much lower material removal rates. The contrast between the two media can be seen in Figure 5.4, where both alumina and cornstarch etch through the green ceramic layer, but the cornstarch is unable to etch the underlying silicon.The powder blasting etch process is relatively anisotropic in nature as the abrasive media is directed in one direction. Some sideways etching does still occur, as the abrasive is not all traveling in one direction due to the divergent nature of the spray and random deflections of the etching media. The edge of the mask may also be deformed or abraded by the etchant, resulting in further degradation of the sidewalls.     These effects can give rise to different etch profiles as the etch area decreases in size. When relatively large-sized holes are etched, the etch front is relatively uniform with only slight edge effects. When the size of the etch hole decreases, the edge effects are extenuated and the etch front becomes less uniform. This is mainly caused by etching media being deflected off the edges of the hole and hitting the base of the depression resulting in a pronounced ‘U’-shaped profile. As the feature size decreases still further, the ability of the abrasive powder to reach the material at the base of the depression decreases significantly, leading to the cessation of the etch process. This is the limit of the achievable resolution and is related to the size of the abrasive particle; the resolution is between 5 and 10 times the particle size. Smaller particles can be used to overcome this issue, but their lower mass means that the kinetic energy available for etching also decreases unless the speed of particles is increased. At a critical point, there will be insufficient kinetic energy for etching to occur.     Ice blasting is a simple, nonabrasive, cleaning process that uses ice crystals as impact medium for removing surface contaminants without the use of chemicals, abrasive materials, high temperatures, or steam. The technology employs ordinary tap water, compressed air and electricity to create an environmentally friendly, cost-effective method for surface cleaning. Ice as a phase change blast medium has the ability to change its physical state to liquid water which flushes contaminants from the surface, leaving no solid residue after blasting. The technique can be used for cleaning surfaces, removing paint, or stripping contaminants from a surface. It can also be used to remove loose material, blips, and burrs from metal components after machining, and even softer materials, such as organic polymeric materials, including plastic and rubber components, can be processed. Compared to other blast cleaning processes, ice blasting does not accumulate ice particles in the waste and thus significantly reduces secondary waste. Applications of ice blasting range from precision cleaning of semiconductor wafers and delicate items, such as books and antiques, to removal of contaminants on a variety of substrates. Ice blasting has been effective in removing paint coatings from a variety of substrates without substrate damage, including delicate surfaces such as Kevlar and graphite-epoxy composites, as well as removing paints, grease, oil, grime, and other contaminants from a variety of glass surfaces, including windows, gauge panels, and controls.

Publish Date: 2021/08/19

Functionalized separator for next-generation batteries

Description:     Functionalized separator for next-generation batteries     Advancements in battery technology have dramatically increased demand for improvements in liquid solid separation design, as the separator plays a critical role in ensuring the safety and electrochemical performance of the cells. Current separators, either in commercial usage or under investigation, have yet to meet the high stability and lifespan performance standards necessary to prevent deterioration in the efficiency and reliability of the battery technologies. Recently, considerable effort has been devoted to developing functionalized separators, ranging from designing a variety of new materials and modification methods, and increasingly, to optimizing advanced preparation processes. In order to understand how the mechanisms of vibrating separator performance are affected by different properties, we will first summarize recent research progress and then have in-depth discussions regarding the separator’s significant contribution to enhancing the safety and performance of the cell. We then provide our design strategy for future separators, which not only meets the requirements of different type of batteries, but also aims for multifunctionality. We hope such a perspective could provide new inspiration in the development of liquid solid separator research for future battery technologies.     The global demand for data storage and processing is increasing exponentially. To deal with this challenge, massive efforts have been devoted to the development of advanced memory and computing technologies. Chalcogenide phase-change materials (PCMs) are currently at the forefront of this endeavor. In this Review, we focus on the mechanisms of the spontaneous structural relaxation – aging – of amorphous PCMs, which causes the well-known resistance drift issue that significantly reduces the device accuracy needed for phase-change memory and computing applications. We review the recent breakthroughs in uncovering the structural origin, achieved through state-of-the-art experiments and ab initio atomistic simulations. Emphasis will be placed on the evolving atomic-level details during the relaxation of the complex amorphous structure. We also highlight emerging strategies to control aging, inspired by the in-depth structural understanding, from both materials science and device engineering standpoints, that offer effective solutions to reduce the resistance drift. In addition, we discuss an important new paradigm – machine learning – and the potential power it brings in interrogating amorphous PCMs as well as other disordered alloy systems. Finally, we present an outlook to comment on future research opportunities in amorphous PCMs, as well as on their reduced aging tendency in other advanced applications such as non-volatile photonics.     Air filter paper with a high filtration efficiency that can remove small-size pollutant particles and toxic gases is vital for human health and the environment. We report a nanofiltration paper that is based on wood fiber filter paper with good mechanical properties and a three-dimensional network structure. The filter paper was prepared by impregnation with multi-walled carbon nanotubes (MWCNTs) and phenol-formaldehyde (PF). The results showed that MWCNTs were present on the surfaces of the fibers and between the pores, which increased the specific surface area of the fibers and enhanced the effective interception of the particles. The optimum impregnation concentration of the MWCNT was 0.1%. Compared with the cellulose fibers (CFs), the average pore diameter of the 0.1% MWCNT–CF filter paper was reduced by 8.05%, the filtration efficiency was increased by 0.64%, and the physical properties were slightly enhanced. After impregnation with PF, the mechanical properties of the air filter paper were significantly enhanced. The PF on the fiber surfaces and at the junction of the fibers covered the MWCNTs. Based on the change in the filter paper properties after impregnation, the optimal filter paper strength index and filtration performance were observed at a solid PF content of 8.4%.     Particles with different sizes and components in the air are in contact with and absorbed by the human body.1 Epidemiological studies have shown a strong correlation between airborne particulate exposure and respiratory disease, cardiovascular disease, and mortality.2,3 Inhalable particulate matter (PM10, aerodynamic diameter < 10 μm) and fine particulate matter (PM2.5, aerodynamic diameter < 2.5 μm) are more likely to carry harmful substances, such as heavy metals or gaseous pollutants, into the human respiratory tract and even the alveolus, causing health hazards.4 Common pollutant control methods include source control, ventilation, and purification.5 Filter paper is an effective material to reduce the concentration of particulate matter in air purification.     Filter paper usually removes particles based on five physical effects: gravity, collision, screening, diffusion, and static electricity.6 The removal efficiency of filter paper is closely related to the relative size of the particle diameter and the paper pore size. Smaller pore sizes of the paper correspond to smaller sizes of the particles that it can intercept under the same filtration efficiency.7,8 Adjusting the structure of the filter paper to improve the air flow resistance can increase the residence time of the pollutant particles in the filter paper, resulting in a higher removal efficiency.9,10 However, the filter filtration resistance directly affects the energy consumption of the pressure leaf filter, such that extremely high filtration resistances are not recommended.11 The filtration efficiency has exhibited dependence on the fiber coarseness. Specifically, finer fibers have exhibited higher filtration efficiencies at a constant pressure drop.12 However, air filter paper must maintain a certain porosity to allow air flow. Nanofibers can increase the specific surface area of the filter paper to generate filter papers with small pore sizes, high filtration efficiencies, and high porosities.     Traditional air filter paper is mainly composed of micron-grade fibers with high air permeability, small airflow resistance, and a poor filtration effect for small particles, which do not meet the requirements of many modern industries for high filtration precision air filter paper. In our work, multi-walled carbon nanotube (MWCNT) air filter paper with a high filtration efficiency and antibacterial activity for extremely small particle pollutants was prepared.13 To reduce the pore size of the filter paper, MWCNTs with large aspect ratios and high specific surface areas were introduced to cellulose fiber (CF) filter paper, which has a low filtration resistance and high mechanical strength due to its porous nanofiber structure.14 The MWCNT–CF filter paper exhibited high air permeability following the incorporation of the MWCNTs. In addition, the MWCNTs exhibited a fine antibacterial ability, which is suitable for industries that require antibacterial, high-efficiency air filter paper.     First, the performance of the CF filter paper was studied after loading MWCNTs with different contents. The MWCNT dispersion (10–15 nm in diameter, 10% concentration) was purchased from Beijing Carbon Yang Technology Co., Ltd., China. CF filter paper (quantitative 90 g m?2) was purchased from Shandong Longde Technology Co., Ltd., China. The MWCNTs were diluted with deionized water to 0.01%, 0.05%, 0.1%, 0.5%, and 1%. The CF filter paper was then dipped into the diluted MWCNT dispersing solution for 30 s and dried in an oven (electric blast drying oven, DGG-101-1, Tianjin Tianyu Experimental Instrument Co., Ltd., China.), with a drying time and temperature of 15 min and 105 °C, respectively.15,16     2.2 Preparation of the PF–MWCNT–CF air vertical pressure leaf filter paper     In this study, phenol-formaldehyde (PF) resin was used to impregnate the MWCNT–CF air filter paper to improve the physical strength of the paper. PF resin (solid content 58%) was purchased from Shanghai Kain Chemical, China. The CF filter paper loaded with 0.5% MWCNTs was impregnated for the second time with PF (dissolved in 99.5% anhydrous methanol). The experiments followed an impregnation time of 30 s, a drying temperature of 105 °C, and a drying time of 15 min. By heating the PF, the gelatinous resin formed a polymer chain resin,17 which gradually hardened from a viscous flow state and appropriately improved the strength of the paper.      2.3 Characterization     The prepared samples were characterized by field-emission scanning electron microscopy (SEM; GeminiSEM 500, Zeiss, Germany), a computer-controlled tensile testing machine (CP-KZ300, Sichuan Changjiang Paper Instrument Co., Ltd., China), and a burst strength tester (969920, L&W, Sweden). The air permeability and pore size distribution of the samples were measured by a digital air permeability meter (YG461E, Ningbo Textile Mill, China) and a capillary pore size analyzer (Porolux 100, Porometer NV, Belgium).     2.4 Filtration performance     The Palas MFP 3000 filter material test system (MFP 3000, Palas Company, Germany) and test dust ISO A2 fine ash were used for testing. The following test conditions were implemented: an end pressure of 2000 Pa, a dust concentration of 1000 mg m?3, a rated gas flow rate of 66 L min?1, a sample area of 100 cm2, and a sample surface velocity of 11.1 cm s?1. The filtration efficiency, filtration resistance, and dust retention of the filter paper were tested.     After the CF filter paper was impregnated with an MWCNT dispersion, MWCNTs adhered to the surface of the vibrating filter paper, thus reducing the pore size and resulting in a higher filter paper surface content compared with that inside the paper. When the load of MWCNTs was greater than 4.56%, the pores readily became blocked, which was not conducive to filtration. At a loading rate of 3.68%, the resistance increased by 26.56% and the dust-holding capacity only increased by 8.33%. At this time, the filtration efficiency was 99.69% (2000 Pa), and the paper strength was also enhanced.     The filtration performance of the MWCNT–CF filter paper impregnated with PF showed little change. The burst index of PF–MWCNT–CF filter paper increased by 110% compared with MWCNT–CF filter paper. The tensile index increased constantly, but the dust retention was too low when the PF solid content was 10%. Thus, the optimal impregnation concentration was 8.4%. At this time, the longitudinal tensile index and transverse tensile index of the filter paper increased by 77.01% and 80.41% respectively, compared with MWCNT–CF filter paper.

Publish Date: 2021/08/19

A view of acrylic

Description:     A view of acrylic     Acrylic plastic refers to a family of synthetic, or man-made, plastic materials containing one or more derivatives of acrylic products acid. The most common acrylic plastic is polymethyl methacrylate (PMMA), which is sold under the brand names of Plexiglas, Lucite, Perspex, and Crystallite. PMMA is a tough, highly transparent material with excellent resistance to ultraviolet radiation and weathering. It can be colored, molded, cut, drilled, and formed. These properties make it ideal for many applications including airplane windshields, skylights, automobile taillights, and outdoor signs. One notable application is the ceiling of the Houston Astrodome which is composed of hundreds of double-insulating panels of PMMA acrylic plastic.     Like all plastics, acrylic plastics are polymers. The word polymer comes from the Greek words poly, meaning many, and meros, meaning a part. A polymer, therefore, is a material made up of many molecules, or parts, linked together like a chain. Polymers may have hundreds, or even thousands, of molecules linked together. More importantly, a polymer is a material that has properties entirely different than its component parts. The process of making a polymer, known as polymerization, has been likened to shoveling scrap glass, copper, and other materials into a box, shaking the box, and coming back in an hour to find a working color television set. The glass, copper, and other component parts are still there, but they have been reassembled into something that looks and functions entirely differently.     The first plastic polymer, celluloid, a combination of cellulose nitrate and camphor, was developed in 1869. It was based on the natural polymer cellulose, which is present in plants. Celluloid was used to make many items including photographic film, combs, and men's shirt collars.     In 1909, Leo Baekeland developed the first commercially successful synthetic plastic polymer when he patented phenol formalde-hyde resin, which he named Bakelite. Bakelite was an immediate success. It could be machined and molded. It was an excellent electrical insulator and was resistant to heat, acids, and weather. It could also be colored and dyed for use in decorative objects. Bakelite plastic was used in radio, telephone, and electrical equipment, as well as counter tops, buttons, and knife handles.     Acrylic acid was first prepared in 1843. Methacrylic acid, which is a derivative of acrylic acid, was formulated in 1865. When methacrylic acid is reacted with methyl alcohol, it results in an ester known as methyl methacrylate. The polymerization process to turn methyl methacrylate into polymethyl methacrylate was discovered by the German chemists Fittig and Paul in 1877, but it wasn't until 1936 that the process was used to produce sheets of acrylic safety glass commercially. During World War II, acrylic glass was used for periscope ports on submarines and for windshields, canopies, and gun turrets on airplanes.     Acrylic plastic polymers are formed by reacting a monomer, such as methyl methacrylate, with a catalyst. A typical catalyst would be an organic peroxide. The catalyst starts the reaction and enters into it to keep it going, but does not become part of the resulting polymer.     Acrylic plastics are available in three forms: flat sheets, elongated shapes (rods and tubes), and molding powder. Molding powders are sometimes made by a process known as suspension polymerization in which the reaction takes place between tiny droplets of the monomer suspended in a solution of water and catalyst. This results in grains of polymer with tightly controlled molecular weight suitable for molding or extrusion.     Acrylic plastic sheets are formed by a process known as bulk polymerization. In this process, the monomer and catalyst are poured into a mold where the reaction takes place. Two methods of bulk polymerization may be used: batch cell or continuous. Batch cell is the most common because it is simple and is easily adapted for making diy acrylic key chain sheets in thicknesses from 0.06 to 6.0 inches (0.16-15 cm) and widths from 3 feet (0.9 m) up to several hundred feet. The batch cell method may also be used to form rods and tubes. The continuous method is quicker and involves less labor. It is used to make sheets of thinner thicknesses and smaller widths than those produced by the batch cell method.     We will describe both the batch cell and continuous bulk polymerization processes typically used to produce transparent polymethyl methacrylic (PMMA) sheets.     The mold for producing sheets is assembled from two plates of polished glass separated by a flexible "window-frame" spacer. The spacer sits along the outer perimeter of the surface of the glass plates and forms a sealed cavity between the plates. The fact that the spacer is flexible allows the mold cavity to shrink during the polymerization process to compensate for the volume contraction of the material as the reaction goes from individual molecules to linked polymers. In some production applications, polished metal plates are used instead of glass. Several plates may be stacked on top of each other with the upper surface of one plate becoming the bottom surface of the next higher mold cavity. The plates and spacers are clamped together with spring clamps.     An open comer of each mold cavity is filled with a pre-measured liquid syrup of methyl methacrylate monomer and catalyst. In some cases, a methyl methacrylate prepolymer is also added. A prepolymer is a material with partially formed polymer chains used to further help the polymerization process. The liquid syrup flows throughout the mold cavity to fill it.     The mold is then sealed and heat may be applied to help the catalyst start the reaction.     As the reaction proceeds, it may generate significant heat by itself. This heat is fanned off in air ovens or by placing the molds in a water bath. A programmed temperature cycle is followed to ensure proper cure time without additional vaporization of the monomer solution. This also prevents bubbles from forming. Thinner sheets may cure in 10 to 12 hours, but thicker sheets may require several days.     When the plastic is cured, the molds are cooled and opened. The glass or metal plates are cleaned and reassembled for the next batch.     The plastic sheets are either used as is or are annealed by heating them to 284-302°F (140-150°C) for several hours to reduce any residual stresses in the material that might cause warping or other dimensional instabilities.     Any excess material, or flash, is trimmed off the edges, and masking paper products or plastic film is applied to the surface of the finished sheets for protection during handling and shipping. The paper or film is often marked with the material's brand name, size, and handling instructions. Conformance with applicable safety or building code standards is also noted.     The storage, handling, and processing of the chemicals that make acrylic plastics are done under controlled environmental conditions to prevent contamination of the material or unsafe chemical reactions. The control of temperature is especially critical to the polymerization process. Even the initial temperatures of the monomer and catalyst are controlled before they are introduced into the mold. During the entire process, the temperature of the reacting material is monitored and controlled to ensure the heating and cooling cycles are the proper temperature and duration.     Samples of finished acrylic materials are also given periodic laboratory analysis to confirm physical, optical, and chemical properties.     Acrylic plastics manufacturing involves highly toxic substances which require careful storage, handling, and disposal. The polymerization process can result in an explosion if not monitored properly. It also produces toxic fumes. Recent legislation requires that the polymerization process be carried out in a closed environment and that the fumes be cleaned, captured, or otherwise neutralized before discharge to the atmosphere.     Acrylic plastic is not easily recycled. It is considered a group 7 plastic among recycled plastics and is not collected for recycling in most communities. Large pieces can be reformed into other useful objects if they have not suffered too much stress, crazing, or cracking, but this accounts for only a very small portion of the acrylic display case boxes plastic waste. In a landfill, acrylic plastics, like many other plastics, are not readily biodegradable. Some acrylic plastics are highly flammable and must be protected from sources of combustion.     The average annual increase in the rate of consumption of acrylic plastics has been about 10%. A future annual growth rate of about 5% is predicted. Despite the fact that acrylic plastics are one of the oldest plastic materials in use today, they still hold the same advantages of optical clarity and resistance to the outdoor environment that make them the material of choice for many applications.     With so many options for clear plastic on the market, it is no surprise that lots of people misunderstand the differences between the types. Each type is made in a different way using different materials, which results in many different price points. We've put together this resource page to help sort out some of the most frequently asked questions, like "is acrylic a plastic or a glass?" and "what is the difference between acrylic and plastic?". While acrylic is a plastic, not all plastic is acrylic. The term "acrylic" represents a family of petroleum-based thermoplastics made from the derivation of natural gas. Another common name for acrylic is "polyacrylate" which is one of the most common types. This material is made from Methyl Methacrylate (MMA), Poly Methyl Methacrylate, or a combination of both.     Although the composition is pretty much the same, acrylic has many brand names. Plexiglas was the original trademark name when the Rohm and Haas Company first introduced the product to a mass market, but many others have established their own brand names including Lucite by du Pont and Acrylite by Evonik Cyro LLC. Some other common brands are Perspex, Oroglass, Optix, and Altuglass.Injection molded acrylic is manufactured by injecting acrylic or polymethyl methacrylate material into a mold. This transparent thermoplastic makes a great alternative to glass, which is why it is commonly used to manufacture bakery bins, sunglasses, and display risers. Unlike polystyrene, injection molded acrylic table number plate can be made without the issues of hazing or coloration. Additionally the material is much stronger and has minimal relief markings when removed from the mold. Injection molding takes less labor than hand-crafting, which results in a lower cost.

Publish Date: 2021/08/19