by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Challenges Faced When Specifying Rotary Shaft Seals for the Food Industry

A good seal should be reliable, experience minimal wear, be easy to install, and enhance equipment performance–but the rotary shaft seals on equipment for food preparation and handling involves much more.

The wrong rotary shaft seal for a food industry application can lead to expensive downtime, costly material waste, damaged equipment, problematic production delays, and even lawsuits. That is why it is critical that the rotary shaft seals that are used in the food industry be carefully specified–which involves several challenges.

Where Are Rotary Shaft Seals Found?

Dynamic rotary shaft seals are a key component for equipment such as …

  • High pressure homogenizers
  • Water purification equipment
  • Meat blenders
  • Distilled water pumps
  • Milk dispensers
  • Ice cream dispensers
  • Food portioning systems
  • Mixers
  • Screw conveyors
  • Milling rice, wheat, and flower
  • Holding tanks
  • Hoppers
  • Crushers
  • Dry product filling systems

Reliable rotary shaft seals are critical for food preparation and handling that includes chocolate manufacturing, baking, beverage manufacturing, bulk material handling, material and poultry processing, feed and grain processing, and dairy processing.

Exposure to Media

Seals in the food industry can be exposed to various types of media, including water, oils, acids, adhesives, powders, semisolids, suspensions, slurrys, and more. Some forms of media, such as acids and slurries, can accelerate the rate of wear experienced by a rotary shaft seal and lead to premature failure if the wrong material is selected. The choice of a material that is compatible both chemically and with the form of media is critical.

Sterilization and Sanitation

Many times rotary shaft seals will be subjected to sterilization procedures for CIP (Clean in Place), SIP (Sterilize in Place) and COP (Clean Out of Place). These methods may require aggressive cleaning agents or disinfectants, superheated steam, and potentially corrosive acids. Finding a suitable rotary shaft seal material that can handle the sanitation and sterilization methods in place for the target equipment can be challenging but not impossible.  

Another potential issue with regard to cleaning involves potential need for seals that can be disassembled and cleaned daily. The ability to spend minimal time in disassembly/assembly can have a significant effect on the cleaning process in terms of time, effort, and the quality of sanitation or sterilization achieved.

Temperatures

As just alluded to, seals may be periodically exposed to extremely high temperatures for cleaning or may simply operate in a high-temperature environment. However, not all temperature concerns relate to high temperatures: some applications involve sub-zero temperatures. The seal and material behavior at the extreme operating temperatures must be considered when specifying seal geometry and material.

Contamination

The food industry can be quite demanding when it comes to rotary shaft seals. Because food is involved, there are a myriad of concerns regarding contamination, with potential sources including lubricants for the seals, contamination from seals that have begun to leak, and contamination from the seals themselves. 

Compliance with Applicable Standards

Any part of a rotary shaft seal that comes into contact with food must conform to regulations such as …

  • USP Class VI
  • FDA 21 CFR 177.1680, 177.1550, and CFR 177.2600
  • (EU) 1935/2004
  • 3-A sanitary standards 18-03 and 20-27
  • NSF/ANSI standard 61 for drinking water systems
  • WRAS BS 6920
  • 3-A Sanitary Standards
  • (EC) No. 1935/2004

And compliance involves more than just the contamination concerns just discussed. The standards and regulations also look at answers to questions such as …

  • Does the material release any chemicals?
  • Does it exhibit outgassing?
  • Does it tend to absorb moisture?
  • Does it react chemically to acidic food ingredients?
  • Can the material be detected or traced?

Conclusion

Issues such as media type, sterilization and sanitation procedures, temperatures, contamination, and regulatory compliance are all challenges faced in the food industry, and that includes dynamic seals for equipment such as mixers and dispensers. Failure to address these issues leads to the premature failure of seals, which in turn leads to material waste, downtime, and production delays as well as the loss of customer confidence and even lawsuits. 

At Advanced-EMC, we understand the challenges involved with specifying rotary shaft seals for the food industry. Our team has the knowledge and experience to assist you in finding the right rotary shaft seal for all your food industry applications. We will work with you to choose a sealing solution that will provide excellent reliability, easy maintenance, and outstanding performance, all while complying with all applicable standards.  

by Jackie Johnson Jackie Johnson No Comments

The Problem with PET Thermoforms

PET thermoform packaging—such as those used for fruits, vegetables, muffins, eggs and more—is technically recyclable with PET bottles. In fact, many PET reclaimers accept thermoforms in bottle bales, as long as auto-sort systems and best practices are in place.

However, only 9 percent of them ever make it to recycling bins.

In this week’s blog post, we will go over the obstacles reclaimers face in recycling PET thermoforms and what the plastics industry has planned to work past them.

A New Law

On September 24th, 2020, Governor of California Gavin Newsom signed a bill made by California Assembly member Phil Tang, requiring manufacturers to include recycled materials when making plastic bottles, and, by extension, plastic thermoform parts.

AB 793 is designed to bolster the market for recycled polyethylene terephthalate in the state. Manufacturers must meet a number of deadlines for recycled content, achieving 15 percent by 2022, 25 percent by 2025 and 50 percent by 2030.

Clamshells play an important role in the ability of companies in California, the country’s largest agricultural producer, to safely ship products across the nation. Lawmakers hope that the bill will propel the whole supply chain toward more environmentally responsible packaging, making California a greener state.

However, opponents of the bill state that while recycled content mandates can be positive, there exists a significant gap between how much recycled content actually exists and the requirements of the bill. Shannon Crawford, director of state government affairs for the Plastics Industry Association, says of the bill:

“While this bill would develop end markets for plastic materials, there should be an equal emphasis on improving the collection and sortation of these materials.”

A New Report

A coalition of packaging and plastic industry groups, part of a project led by the Foodservice Packaging Institute, and includes the Association of Plastic Recyclers, the National Association for PET Container Resources and companies like Amcor Ltd., Driscoll’s Eastman Chemical Co. and Sonoco Plastics, released a report in December on pathways to try to increase PET thermoform recycling. The report estimated there to be around 1.6 million pounds of PET thermoforms used in packaging in the United States and Canada. That, also according to the report, is sufficient enough to sustain a recycling market.

The problem, it found, was that there were also sizable barriers. These include technical challenges that cap the amount of PET thermoforms that can be mixed in with bales of more valuable PET bottles. On top of that, the prices of virgin resin have lowered to the point of creating a competitive challenge. And while buyers of PET bottles are willing to pay a premium, that’s not the case with other PET markets such as thermoforms.

According to Resa Dimino, senior consultant at Resource Recovery Systems, which prepared the report for the industry coalition, the next phase after the report will be to develop a pilot project in a community and work with MRFs and others on technical challenges. It will also include developing a viable investment strategy for PET thermoform recycling.

In Conclusion

While it is clear that thermoforms can be recycled, we still have a long way to go before the process is viable for the industry as a whole. The good news is that the industry is increasingly moving towards more sustainable options.

by Jackie Johnson Jackie Johnson No Comments

Rising Prices of Polymers

In North America, prices for polyethylene, PVC and other solid polystyrenes have risen to unprecedent highs in 2021. This is due to a variety of factors, the most common being a distinct lack of materials used to make the plastics. Whether due to the pandemic, a mechanical failure, or simply being unable to keep up with the demand, it is clear that the scarcity of materials is causing an increase in prices.

In this week’s blog post we will go over several different polymers and why the prices have hiked in 2021.

Climb in Prices

Regional PE prices climbed an average of 9 cents per pound since April 1st of this year. Due to the pandemic and by outages caused by Winter Storm Uri in February, supplies of the material remain increasingly scarce. Some grades are harder to find than others. For example, high density PE for blow molding has been particularly hard to find, to the point where work has been delayed.

PE market analyst Mike Burns of Resin Technology Inc in Fort Worth, Texas says that allocations are moving higher than 70 percent, however demand is still vastly exceeding supply.

Force Majeure

On top of the already scarce supply of materials, North American PE supplies are further strained by a mechanical failure at a Nova Chemicals Corp. production site.

In April of this year Nova was forced to declare a force majeure, a term where an unforeseeable circumstance has prevented someone from fulfilling a contract, which covers all PE resins produced in the Sarnia, Ontario region. This includes low density PE, HDPE, and more.

A Nova spokesperson said in a letter released to the public that the firm “has experienced a mechanical failure beyond our control…. Which supplies ethylene to our polyethylene facilities…”

According to the spokesperson, there were no injuries or environmental impacts from the event, and that they did not know how long the force majeure would be in place.

PVC

With limited supplies and strong demand, PVC prices have risen by 4 cents per pound in April. Because of Winter Storm Uri, PVC makers have had a hard time finding supplies of stabilizers and other additives needed to make PVC compounds, contributing to the ever-tight supply of PVC.

This has hit the construction market has been hit particularly hard by the lack of product, with housing starts at a whopping 1.74 million rate for March, up by almost 40 percent compared to March 2020.

Prices for suspension PVC are up by 21 cents as of May 2021, up a net of 33.5 cents per pound since January of 2020.

PS

As a result of higher prices for benzene feedstock, where prices were up 38 cents for the moth to $3.01 per gallon, prices for solid PS (solid polystyrene) have surged to 9 cents per pound.

Solid PS prices for this year are up 25 cents, and 37 cents as of last year. Benzene prices are up 78 cents in the last two months alone, an increase of almost 35 percent.

The reason for this dramatic price increase? Styrene and benzene supplies have been limited. Some Gulf Coast styrene operations are only operating at 50-60 percent in recent months.

Other Materials

There are several other plastics that have seen an increase in cost of the past few months. Nylon 6 is up an average of 15 cents with Nylon 6/6 up by 25 cents. As of the first of the year, polycarbonate and ABS are both up an average of 30 cents.

On a Positive Note

Despite the increase in prices, the demand for polymers has not slowed down in the slightest. In 2020 alone, the market size was valued at USD 579.7 billion. That number has increased to USD 594 billion by 2021, with an estimated net worth of USD 750.1 billion by 2028. That is a growth rate of 3.4%!

The demand is clearly there, and it is safe to say that once the supply issues have been solved, the price of plastics will once again level out.

In Conclusion

Prices for polymers has increased over the past few months due to a variety of circumstances ranging from mechanical failure to the global pandemic. Despite this the plastics industry has remained steadfast and continues to innovate and provide quality products.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

All About Automolding

PTFE is an excellent material for many different applications and operating environments. Its low friction, chemical compatibility, and ability to maintain key properties at extreme temperatures has made it ideal for everything from seals in sterile food handling equipment to sleeve bearings in the harsh world of oil and gas

And there are several different options when it comes to manufacturing PTFE components, but not all methods are the same. In this blog post, we will be discussing auto molding in the context of manufacturing PTFE components.

What is Auto Molding?

Auto molding, as known as compression molding, is a popular manufacturing technique for making thermoset and thermoplastic parts–and one of the oldest plastic forming methods still in use. In short, auto molding uses compression and dies to form a near net shape polymer part. 

Where is Auto Molding Used?

There are numerous industries that depend on auto molded parts, such as aerospace, chemical processing, and the manufacture of semiconductors.

Auto molding is used to manufacture a wide range of parts, as well. These include …

  • Bearings
  • Bushings
  • Piston rings
  • Sleeves
  • Seals
  • Gaskets
  • Valves
  • Valve Seats
  • Diaphragms
  • Bellows
  • Electrical components

When compression molding of a PTFE part is done correctly, then you can depend on key aspects such as specific density, strength, elongation, and flex life as well as permeation resistance.

How Auto Molding Works

In the auto molding process, the raw materials are in the form of molding compounds. These molding compounds may be preforms (which is already shaped somewhat like the final part), granules, or putty-like masses. 

The basic design for the mold is usually generated from a 3D CAD file, and the tool and die maker will then base the mold design on that file. However, the mold designer must account for shrinkage, molding compound flow, size and positioning of channels to carry away excess material, and achieving uniform curing temperatures for the part. It is also important to ensure that the part can be removed from the mold, and there may be a need for ejector pins to achieve this. Needless to say, the mold is the most expensive aspect of auto molding.

Once the mold design is complete, it is manufactured out of steel using a CAD/CAM (Computer-Aided Design / Computer Aided Manufacturing) system and a CNC (Computer Numeric Control) milling machine. Additional features and surface finishes may require post-processing of the mold.

Once the mold is ready to go, the amount of compound needed for the part is carefully measured out and placed in the pre-heated open mold cavity. Once in place, the other side of the mold closes over the mold cavity and pressure is applied (most often by a hydraulic ram) in one direction to force the raw materials to fill up all cavities within the mold. Any excess material is carried away from the mold via overflow grooves.

Heat and pressure are both maintained until the polymer has completely cured. Once the part has cured and cooled, it is removed from the mold, and this part of the process may require the use of part ejection pins to completely free the newly cured part from the mold. After the part is removed, any flash can be easily trimmed away and precision machining can be used to ensure the part meets necessary tolerances.

Auto Molding PTFE

There are certain key aspects to auto molding PTFE compounds, including …

  • Pressure (usually between 3,000 and 4,500 psi)
  • Sintering temperature (in the range of 685°F – 720°F)
  • Dwell time (how long the part is held at the sintering temperature)

Pressure and dwell time are dependent on the volume and geometry of the part, as well as the machine being used.

Benefits of Auto Molding 

Auto molding PTFE has numerous benefits:

  • Range of geometries and shapes are possible
  • Can produce larger parts than possible with extrusion
  • Minimal waste material
  • Very cost-effective when compared to injection molding
  • Good surface finish
  • Close tolerances
  • Avoids defects associated with machining a polymer (e.g., internal stresses, warping)

In addition, auto molding can be used with both virgin and filled PTFE. Fillers can include both those that enhance structural and material properties (e.g., carbon fiber, molybdenum disulfide MoS2) and colors. Depending on the size and geometry of the part, it may be possible to compression mold multiple parts simultaneously. In such cases, a multi-cavity die would be used.

Disadvantages of Auto Molding

However, there are pros and cons to every PTFE manufacturing process. In the case of auto molded PTFE, the production speed is slower compared to injection molding (due to longer cycle times). Flash will always form and needs to be removed before the part can be considered finished, and this can also add a bit to the production time. While compression molding can be used to manufacture complex parts, there can be issues, such as underfilling in certain areas and the inability to achieve undercuts.

Auto Molding Costs

The most expensive aspect of auto molding, aside from the machinery needed, is the compression molds. Mold cost depends in part on the size of the component, but is more heavily influenced by the complexity of the die. The more complex the geometry of a part, the more expensive the die will be. However, the cost of a compression molding die is significantly less than that of an injection molding die. This is mostly due to the fact that compression molds do not require a complicated system of gates and runners that are necessary in injection molds.

Conclusion

Auto molding works well for manufacturing PTFE components that are not overly complex, have no undercuts, and involve a medium to large production run. In addition, the auto molding process is generally far more cost effective than injection molding. However, for PTFE parts to be high quality and durable, you need a company that is familiar with the process.

At Advanced EMC, we have the knowledge and experience to assist you with auto molding PTFE parts for your applications. Contact us today if you have any questions or are interested in obtaining a quote.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Injection Molded and Machined PEEK Components

PEEK (polyetheretherketone) is a high-performance thermoplastic available in various grades to suit a wide variety of applications. It is commonly used in bushings, medical implants, gears, gaskets, and more. However, what one of the aspects of PEEK that makes it stand out from other engineering polymers is that it can be machined or injection molded, making it suitable for the manufacture of an even more diverse group of components.

PEEK Components

There are a number of different types of parts and applications where machined or injection molded PEEK are used. These include …

It is also a common material in a variety of industries, including …

  • Oil & gas
  • Renewable energy
  • Nuclear energy
  • Chemical processing
  • Food & dairy
  • Medical
  • Pharmaceutical
  • Transportation
  • Electronics (including semiconductors)
  • Aerospace

PEEK: High Performance Polymer

PEEK is both stiffer and stronger than most plastics, retaining its mechanical strength even at high temperature. It also provides key characteristics such as dimensional stability, excellent wear resistance, and hydrolytic stability. It is also known for having a low coefficient of friction, self-lubrication, and a very low tendency to form stress cracks. PEEK also provides very good chemical resistance and is insoluble in most solvents. In addition, it provides both environmental and regulatory benefits because it is fully recyclable. Furthermore, PEEK lends itself to various processing methods.

PEEK is available in FDA-approved grades as well as implantable grades, where its biocompatibility makes it highly desirable for medical applications. In addition, PEEK grades are available that can handle gamma radiation exposure and even autoclaving as part of sterilization processes. It is ideal for very harsh, high temperature environments, including those found in the petrochemical industry and aerospace. Its low particle generation and outgassing make it well adapted to applications involving semiconductors where high purity is critical.

Fillers can also be added to PEEK to improve properties such as abrasion resistance, surface hardness, and friction. Common fillers include glass, carbon, and graphite fibers as well as PTFE and silicon dioxide. Glass fibers can increase compressive strength and enhance heat resistance while carbon and graphite fibers reduce weight while increasing overall strength. Adding PTFE to PEEK further reduces friction while silicon dioxide can be used to increase strength.

Injection Molded PEEK

Injection molding involves raising the temperature of a polymer to the point where it almost melts, which allows it to be injected under high pressure into a mold. Once the polymer has cooled, the components are removed from the mold and typically require minimal post-processing to prepare them for use.

Injection molding PEEK is much cheaper than machining for larger  production runs around 10,000+ components, and is a near-net-shape manufacturing method that results in minimal waste. It works extremely well when parts are needed that are too complex to machine efficiently. The most costly aspect of injection molding lies in the design and execution of the molds required; however, depending on the size of the part and the machine used, multiple parts can be injection molded with a single die.

When used in connection with PEEK, injection molding is often used to manufacture a replacement for metal bushing. Injection molded PEEK bushings can be found in various applications, including …

  • Citrus processing, where exposure to the acids in the fruit can lead to chemical compatibility issues
  • Pumps used in harsh environments that include aggressive chemicals and high temperatures
  • Applications where the presence of vibration accelerates wear

Note, however, that injection molding PEEK involves very high processing temperatures that not all facilities are equipped to handle. In addition, to achieve reliable part fabrication, there are certain cooling requirements that must be met to prevent issues such as warping and annealing may be required to eliminate residual stresses. Injection molding is also limited in its capabilities when there is a need for high precision parts or large parts.

Machined PEEK

Machining using cutting and grinding tools to remove unwanted material from a solid blank in order to produce the desired component. Most facilities use CNC (Computer Numeric Control) machining, which ties in well with CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) that allows a part to be first designed on a computer and then machined using tools that are computer controlled.

Machining is typically used when dimensions need to be extremely precise, the geometry of the PEEK component does not lend itself to injection molding, thin walls are needed, or the desired components are relatively large.

Machining is also more economical when a short production run (<5,000) is involved, which means it is also ideal for developing prototypes. It is faster than injection molding because there is no significant upfront time required for tooling such as molds / dies. In addition, machined PEEK parts usually have much better wear and mechanical properties than injection molded PEEK. And, unlike many thermoplastics, PEEK is easy to machine. Machining also works extremely well for achieving thin walls and fabricating parts with non-standard dimensions or shapes.

There are several industries that make use of machined PEEK components, including …

  • Oil and gas industry, where large PEEK bushings are often required
  • Medical applications where an FDA-approved material must be combined with high precision, customized parts
  • Arctic wind turbines, which require large bushings that can handle the aggressive environment 

Machining can be challenging when working with a filled grade of PEEK and not all machining companies have the skills and knowledge needed to fabricate a machined PEEK component. Finally, annealing may be needed to stress relieve machined parts.

Conclusion

For PEEK parts with a short production run that require a short lead time, machining works extremely well. It is also recommended when there is a need for thin walls or extreme tolerances. On the other hand, high-production volumes will benefit from the lower costs involved with injection molding. 

Advanced EMC has the skill and equipment needed for precision machining and injection molding of PEEK components. To learn more about what we have to offer or to get advice on which process would work best for your application, contact us today.

 

by Jackie Johnson Jackie Johnson No Comments

The Mexican Plastics Industry During COVID-19

With COVID-19 spreading across the globe, one company in Mexico City has created a rotomolded solution to help curb the infection in one of the world’s largest food markets. In fact, Mexico’s plastics industry has played a large part in COVID-19 relief.

The Mexican plastics industry is a relatively young one. However, it has quickly become one of the fastest developing sectors in the country. In 2016, the country was the tenth largest worldwide plastic producer, with a market of $33 billion.

Because it is so new, the Mexican plastics industry has the unique advantage of having new machinery that is on par with, and even superior to, those in Europe, where equipment could be 50 years old. Which means there are fewer problems to contend with which in turn allows for rapid production and innovation when the country needs it most.

So, in this week’s blog post, we will cover how the Mexican plastics industry has combated COVID-19.

Hospitals and Hand Washing Stations

The Mexico City based company Grupo Rotoplas SAB de CV has teamed up with toilet cleaning brand Harpic as well as the Mexican Red Cross to install a field hospital at the Central de Abastos, an open-air food market in the borough of Iztapalapa in central Mexico City, which was considered in the early days of the pandemic to be one of the main sources of contagion in the city. The hospital has been able to provide tests and care for sufferers of COVID-19.

Developed in the 1970s, Iztapalapa is one of Mexico City’s sixteen municipalities, and with a population of 1.8 million it is the most populous. The borough is heavily working class, and the people of Iztapalapa have been still working on the streets even while the threat of the Corona virus looms. When COVID hit the Central de Abastos, it spread rapidly, with one testing center testing 15,000 people with 1,347 testing positive.

In response, in addition to the field hospital, Rotoplas has installed multiple hand washing stations across the market, which covers 800 acres, as well as hanging banners offering advice on preventative action. Because of this it is estimated that 12,000 people have benefited from the new sanitary measures.

Rotoplas is best known for manufacturing large water tanks. They have a 27 product lines operate a score of manufacturing facilities across North and Central America and employs about 3,000 people.

From Coca-Cola to Face Masks

Like most of the world, Mexico has had a hard time procuring masks for hospitals and other medical facilities. One company, food-grade PET recycler PetStar SAPI de CV, stepped up to the plate by donating around 212,000 20-calibre face shields made from 1-million plastic bottles, which in turn were donated by Arca Continental, a company that is part of the Mexican Coca-Cola industry.

The process of recycling plastics is a labor intensive one. The plastic must first be washed to remove impurities that could impede operation. Then the plastic is fed into shredders which break down the plastic into much smaller pieces. These smaller pieces can be processed into the next stages for reuse. Before that, they must be checked again for any remaining impurities and given a second wash. After the plastic is further tested and identified by class and quality, they are melted down and crushed together to form pellets. These pellets can then be molded to form items such as face shields.

Recycling plastic bottles not only helped provide more masks to frontline workers, it also kept plastic bottles out of landfills and the ocean, where they could linger for generations. Not only did PetStar provide life-saving face masks, they also helped reduce plastic waste by recycling bottles.

Much Needed Protection

Dow Inc. contributed 25,000 protective gowns to the health sector of Mexico. For healthcare professionals battling COVID-19, isolation gowns are among the most used personal protective equipment right behind masks. And like masks there has been a shortage. In response, DOW, Inc. collaborated with nine key partners across a multitude of industries to develop donate 100,000 isolation gowns to frontline workers in Texas, Louisiana, and of course, Mexico.

Michelle Boven of Dow, Inc. had this to say on the subject:

“Many companies have shown tremendous ingenuity and speed in changing over production to meet the needs for respirators, masks, face shields, hand sanitizer and other products critical to fighting this pandemic,” said Boven from Dow. “With the accelerated product development, testing and certification of these medical gowns, Dow is proud to be among these innovators and we will continue to look for ways to use our vast material science expertise to address the needs of frontline workers around the world.”

Other Examples

  • Chemical manufacturer Alpek SAB de CV donating 500 gallons of hand sanitizing gel to public hospitals.
  • Polyethylene maker Braskem Idesa S.A.P.I. donated 12 metric tons of PE for the production of one million bottles of disinfectant.

In Conclusion

Mexico’s plastic industry is relatively young, but still booming despite the pandemic. It has expanded rapidly to become a $33 billion industry. With the increase in growth the Mexican plastic industry has been in the unique position to help the people of Mexico withstand the deadly pandemic.

Whether it’s providing lifesaving protective equipment or simply placing banners with tips on how to stay safe, the plastics industry has stepped up to help during these uncertain times.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Polymer Seal Options for Semiconductors

The manufacturing of semiconductors and semiconductor-related products requires reliable, high purity seals that can survive harsh operating conditions. The right sealing solution can reduce downtime, increase production efficiency, reduce power requirements, and increase process reliability

Seal Environments in Semiconductor Applications

The operating environments for seals in semiconductor applications are challenging to say the least. They may be exposed to fluorine and oxygen plasmas, as well as chlorinated gases, at extreme temperatures or vacuum conditions. Semiconductor seals are typically exposed to highly aggressive, corrosive fluids, such as acids, bases, amine-based strippers, and solvents. Such operating environments can quickly lead to seals that fail prematurely or experience rapid degradation. In addition, because of the delicate nature of semiconductors with respect to contamination, most applications require ultra-high levels of purity.

Semiconductor Applications for Seals

  • Semiconductor processing systems
  • Rotary shaft seals for gearboxes and processing pumps
  • High speed seals

Key Material Properties for Semiconductor Seals

When it comes to semiconductor seals, there are certain material properties that are often key:

  • Reliable mechanical performance
  • Extremely low levels of both anionic and cationic impurities
  • Low levels of TOC (Total Organic Carbon) 
  • Good performance in ultra pure deionized water
  • Low permeation rates
  • Reduced IR (Infrared Absorption)
  • Resistance to both dry and wet process chemistry
  • Minimal outgassing (which can be a major problem at continuous high temperatures)
  • Minimal particle generation 
  • Ultra-high purity
  • Low friction 

Types of Semiconductor Seals

While some applications may simply need a more traditional lip seal, other options include labyrinth seals, spring-energized seals, and encapsulated o-rings. 

Labyrinth seals are a type of dynamic mechanical clearance seal that, when the right material is chosen, exhibit very low friction and provide a long seal life. They are most often used to isolate an area of low pressure from an area of high pressure and do an excellent job of keeping problematic contaminants out and fluid media inside. Labyrinth seals perform extremely well in the presence of extreme pressures as well as cyclic temperatures and pressures. They are also available in a wide variety of engineering polymers, including those recommended for semiconductor seals.

Spring-energized seals can handle vacuum pressures and extreme temperatures extremely well, maintaining a reliable seal when lip seals or o-rings fail. This is made possible by a spring energizer that causes the lip of the seal to maintain contact with the sealing surface even when there are varying pressures or dimensional changes. These are highly dependable seals and can work well in semiconductor applications when combined with the right spring and lip material. 

Encapsulated o-rings work especially well in cryogenic applications and are able to maintain seal integrity in axial sealing applications that are extremely challenging to other seal types. In this type of seal, an elastomeric or spring core is completely contained within a polymeric o-ring, and (once again) with the right material choices can provide outstanding performance even in the presence of highly corrosive or reactive materials. In addition, non-contaminating materials such as PTFE are often used in encapsulated o-rings.

Polymer Materials for Semiconductor Seals

While the type of seal used (i.e., labyrinth, spring energized, etc.) is vital to your design, the choice of material is vital to ensure that the seal does not degrade or prematurely fail. There are several engineering polymers that are well adapted to the unique challenges faced by seals in a semiconductor environment.

PEEK (Polyether Ether Ketone) already has an excellent reputation as a seal material for general applications due to its low friction, wide range of operating temperatures, and excellent chemical resistance. In the context of seals for semiconductors, it also exhibits key features such as low outgassing, good plasma resistance, and excellent performance at high-service temperatures. 

PTFE (Polytetrafluoroethylene) is another very popular seal material, sharing several characteristics with PEEK along with even lower friction and superior chemical compatibility. PTFE works extremely well in high temperature, corrosive environments and is a high-purity material. Note that PTFE is already a commonly used material for gaskets in semiconductor applications.

PI (Polyimide) is another excellent option for semiconductor seals. It is another high purity material that exhibits low outgassing and excellent cryogenic performance along with other properties that are needed to ensure excellent seal integrity. 

Another potential material for use in sealing applicants for semiconductors is PCTFE (Polychlorotrifluoroethylene), often known by its trade name Kel-F or Neoflon. PCTFE shares many of the characteristics of PTFE while improving on others, including better strength and hardness. Like PTFE, it also offers low friction and excellent chemical compatibility.

PAI (Polyamide-imide), referred to by its trade name Torlon, is another option when looking for the right material in semiconductor sealing applications. It is another polymer that has excellent sealing properties when cryogenic temperatures are involved and high pressures are involved. It is also chemically compatible with a range of corrosive media and has excellent wear resistance combined with self-lubrication and low friction. 

Conclusion

Specifying seals for semiconductor applications can be extremely challenging, but the right combination of seal type and material can increase operational efficiency, reduce equipment and process downtime, and lower overall maintenance and operation costs. If you are interested in further exploring sealing solutions for semiconductor applications, our knowledgeable team of seal experts here at Advanced EMC can work with you to find the optimal seal for your design.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

The Basics of Ball Valve Seat Materials

Ball valves play a critical role in controlling the flow of fluid and pressure within a pipeline, but their effectiveness and safety is only as good as the seat material used. In this blog post, we are going to review the basics of five commonly used ball valve seat materials.

Ball Valves

Whether found in a petrochemical application where a leak could be environmentally devastating, or in a pharmaceutical laboratory where cleanliness and sanitation are critical, ball valve seats must be reliable and robust. A ball valve consists of the body of the valve, the body cap, the stem, the hollow ball, and the round ball valve seat. 

The ball valve seat is responsible for sealing the fluid inside and uniformly distributing the seating stress. In soft seat ball valve designs, either an elastomer or polymer is used as the seal and are inserted into a metallic seat ring. This approach, as opposed to hard seat ball valves, is popular because it provides good sealing action, is lighter weight, and more cost effective. 

Key Properties of Ball Valve Seat Materials

When choosing a polymer material for a ball valve seat, there are numerous factors that are involved. Key material properties include …

  • Sufficient ductility to provide a reliable seal
  • Dimensional stability to ensure the ball valve seat retains its shape for reliable sealing and performance
  • Very low friction to keep stem torque at a minimum
  • Low coefficient of thermal expansion so that the ball valve seat retains its shape when temperature changes occur
  • Excellent wear resistance for a long service life
  • Chemical compatibility with all media involved 

In some operating environments, it is also important that ball valve seat materials exhibit these properties:

  • Low moisture absorption to prevent dimensional changes in the presence of water or high humidity
  • Maintain performance with repeated sterilization that can include hot water, steam, and harsh cleaning chemicals
  • Good performance in the presence of sudden decompression (i.e., pressure drops over 650 psi)

Recommended Materials for Ball Valve Seats

There are several materials that work well as ball valve seats, including acetal, PEEK, PTFE, TFM, and UHMW-PE.

Acetal Ball Valve Seats

When aggressive environments are involved, Acetal (also known as Delrin) is often used. Acetal provides excellent wear resistance, is very rigid, has good toughness, and is resistant to cold flow. Although its operating temperature range is not very wide (-70°F to 180°F), it can handle pressures up to 5,000 psi. Acetal also works well in radioactive environments  but should not be used with oxygen flow.

PEEK Ball Valve Seats

PEEK offers excellent chemical resistance, very low friction, self-lubrication, and is flame retardant while also possessing a wide operating temperature range (from -70°F to 550°F). It can handle very aggressive applications and works well when there is a need for hot water and steam exposure–but does not do well in the presence of sulfuric acid.

In addition, PEEK is very well adapted to nuclear applications and is available in FDA-approved grades as well as filled grades with improved wear properties and better thermal conductivity. Note that PEEK is usually chosen for ball valve seats when the operating temperature range is outside that of PTFE.

PTFE Ball Valve Seats

PTFE (also known by its trade name, Teflon) has many of the same properties as PEEK, but involves even lower friction, dry running capabilities, and more extensive chemical compatibility. Like PEEK, it is available in FDA-approved grades and can handle cryogenic temperatures down to -50°F and high temperatures up to 550°F as well as pressures up to 5,000 psi.  \

Also like PEEK, PTFE can continue to perform even when repeatedly exposed to hot water and steam. Keep in mind, however, that PTFE does not perform well in the presence of fluorine or alkalies. PTFE is also very easy to clean and available in glass or carbon-reinforced grades that can provide improved wear characteristics, less propensity to cold creep, and lower thermal conductivity. 

TFM Ball Valve Seats

TFM (sometimes referred to by the brand name Dyneon) is a second-generation PTFE material that combines the best properties of PTFE (low friction, chemical resistance, high-temperature performance) with better stress recovery and the ability to handle higher pressures. It is also more elastic and resilient than PTFE. The operating temperature of TFM ranges from -100°F to 450°F and it is well adapted to applications involving steam and thermal fluids.

UHMW-PE Ball Valve Seals

UHMW-PE, which stands for Ultra-High Molecular Weight Polyethylene, has a low coefficient of friction, an operating temperature ranging from -70° F to 200°F, good chemical resistance, good dimensional stability, and good abrasion resistance. In general ball valve seats made from UHMW-PE can handle pressures up to 1,500 psi and can handle low to medium levels of radiation exposure.

Conclusion

Ball valve seals are used in many different industries, including chemical processing plants, oil and gas operations, manufacturing facilities, food preparation, and even residential use. As a leak-proof means of pressure and flow control, their smooth and reliable operation is critical–which is why polymer materials work extremely well for ball valve seats. If you are in the market for a ball valve seat material, contact the experts at Advanced EMC. We can put our years of experience to work for you, helping you select the right material for your project.

 

by Jackie Johnson Jackie Johnson No Comments

Benefits of PTFE For Sealing Applications

PTFE (Polytetrafluoroethylene), also known by its trade name Teflon, is a polymer material commonly used in sealing applications that offers unparalleled stability and sealing characteristics across an extremely wide range of temperatures, from the extreme heat of a space shuttle engine to the cryogenically cold temperatures used to preserve

In this article, we will discuss how and why PTFE is one of the best materials to use for seals in a wide variety of applications.

Low Friction

PTFE has the highest melting point and lowest friction, and is the most inert of all the fluoropolymers. It has a continuous service temperature rating of 500 degrees Fahrenheit. Molding powders are excellent, fine cut granular resins, well suited for a variety of demanding chemical, mechanical, electrical and non-stick surface applications.

Such applications include:

  • Cookware
  • Outdoor Rain Gear
  • Medical Devices
  • And more!

Cryogenic Applications

Cryogenic seals are used with super-cooled media, like liquid hydrogen or compressed natural gas, at temperatures below -238°F and down to -460°F (absolute zero). Cold temperatures like this are rough on a seal because at these temperatures most materials begin to exhibit highly brittle behavior and lubricants typically cannot be used because they will freeze. PTFE seals, however, can handle temperatures all the way down to -450°F and are capable of dry running because of their extremely low friction. PTFE cryogenic seals are used in industries like oil & gas, pharmaceuticals, and aerospace.

High Temperature Applications

PTFE seals work well at the other end of the spectrum, too. They can continue to function in extreme temperatures up to 600°F, and continuous operating temperatures up to 600°F. Note that a filler may be required to enable the PTFE to dissipate heat more quickly. It’s not uncommon to see PTFE seals in petroleum or steam applications where temperatures greatly exceed 200°F.

PTFE is also non-flammable, making it ideal for use in applications such as jet propulsion engines. Where other materials would simply melt under the pressure of constant exposure to high temperature flames, PTFE is built to withstand even the hottest of environments.

The use of seals for high temperature applications include oil and gas industry and aerospace, to name a few.

Chemical Applications

The chemical resistance of PTFE is some of the best on the market. It is stable in most aggressive and corrosive media, including:

  • Acetone
  • Chloroform
  • Citric Acid
  • Hydrochloric Acid
  • Sulfuric Acid
  • Tallow
  • Sodium Peroxide
  • And more!

However, it should be pointed that that PTFE is not chemically resistive to liquid or dissolved alkali metals, fluorines and other extremely potent oxidizers, as well as fluorine gas and similar compounds. Outside of those, PTFE is an excellent choice for applications involving chemicals.

Oil and Gas Industry

Seals are critical for the safe and reliable operation of oil rigs across the globe. Not only do seals need to be able to withstand a wide variety of extreme temperatures, but they need to be able to handle extreme pressures as well. For well drilling, for example, seals need to handle pressures from 345 to 2070 bar (5000 to 30000 psi).

For those reasons, PTFE is an incredibly popular material to make oil and gas seals out of. Because of it’s resistance to heat, cold and high pressure, PTFE can withstand the rigors of oil and gas unlike any other material.

Spring-energized Seals

In order to retain sealing power under extreme temperatures, many engineers and designers go with spring-energized PTFE seals. The spring provides optimal sealing by forcing the lip of the seal against the mating surface and helps to account for dimensional changes as a result of temperature fluctuations.

A highly efficient seal is created as the system pressure increases enough to take over from the spring and engage the shaft or bore. The spring or energized seal assembly provides permanent resilience to the seal jacket and compensates for jacket wear, hardware misalignment and eccentricity. The jacket material is critical in design to assure proper seal performance.

Rotary Shaft Seals

Using PTFE in rotary shaft seals allows them to be able to run at higher pressures and velocities when compared to other materials. They are also able to have tighter sealing, often exceeding 35 BAR and can run at far more extreme temperatures ranging from -64 degrees Fahrenheit (-53 degrees Celsius) to 450 degrees Fahrenheit (232 degrees Celsius).

On top of that, they are:

  • Inert to most chemicals
  • Can withstand speeds up to 35 m/s
  • Compatible with most lubricants
  • Come in a wide range of sizes
  • And more!

Conclusion

PTFE is an ideal sealing material for both extremely high temperature applications and demanding cryogenic applications. It retains its key sealing properties: stiffness, strength, dimensional stability (may require spring energizer), low friction, and chemical compatibility- even in the most aggressive operating conditions.

Need PTFE sealing solutions? Advanced EMC Technologies is the leading provider of PTFE spring energized and rotary shaft seals in the US. Contact us today!

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

7 Things to Know About FlexForce Canted Coil Springs

FlexForce canted coil springs have special characteristics that make them useful in a variety of applications, ranging from locking components together in an orthopaedic implant to providing an energizer for mission critical aerospace applicants. In this blog post, we will introduce seven key facts about FlexForce canted coil springs that you need to know.

Are a Specific Design for Springs

Canted coil springs, also known as slant coil or cant coil springs, are springs that have the individual coils set at an angle to each other, rather than having them all parallel. This coil configuration significantly impacts the performance of these springs and makes them ideal for a wide range of uses.

What makes canted coil springs different from other types is the fact that they have a flat load curve when they are compressed. Because of this, canted coil springs generate predictable loads throughout their wide deflection range.

Can be Used as Mechanical Connectors

Canted coil springs are ideal for applications that involve latching, locking, or holding to connect two components (also known as detent mechanisms). Latching involves fastening two parts together so that they can still be disconnected when needed. Locking creates a permanent connection that can only be broken by damaging the sea. Holding, on the other hand, both retains and aligns parts and makes sliding possible via the controlled spring force. 

Canted coils are commonly used to connect two mating surfaces in a highly predictable, repeatable fashion thanks to the flat load curve. When canted coil springs are used, the insertion/removal force can be engineered to a high degree of accuracy.  And when used as a latching, locking, or holding connector, FlexForce canted coil springs provide a lightweight, high strength option that can be used for practically an infinite number of cycles.

Can Provide Exceptional EMI/RF Shielding

One of the common uses of canted coil springs is their ability to effectively provide EMI/RF shielding. Furthermore, the electrical properties of these springs can be customized to provide more optimal shielding against certain ranges of conductive and radiated interference.  

Add to this the fact that they can adapt to irregular and uneven shapes to provide consistent shielding, and it is easy to see why they are a common choice for applications that need to be protected from harmful electromagnetic and radio frequency crosstalk interference.

Can Act as a Multiple Point Electrical Conductor

Some designs depend on multiple electrical contact points, which a canted coil can provide. Using a canted coil spring for electrical connections results in a reliable connection that results in a cooler operation temperature. It allows engineers to manage more power in compact spaces and provides both conducting and grounding capabilities in both static and dynamic applications. In addition, canted coil springs as electrical conductors can perform in some of the harshest operating environments that may involve vibration and shock. It should come as no surprise that canted coil conductors are often used in medical applications inside the human body.

Can be Used with Spring Energized Seals

Canted coil springs work extremely well as the energizer in spring-energized seals. Because of the energizer, spring energized seals are able to maintain contact with the sealing surface, even if issues such as out of roundness, uneven mating surface, runout, hardware gaps, eccentricity, or seal lip wear are present. 

The flat load curve of these springs also means that friction stays fairly consistent in dynamic sealing applications. This makes them ideal for sealing situations that involve critical friction and torque specifications. In addition, canted coil springs are very unlikely to experience compression set. 

Available With a Range of Options

There are several options for canted coil springs. They are available in varying levels of spring force: light, medium, and heavy. And canted coil springs come in both standard and custom sizes. As to the spring wire itself, they are available in wire diameters between 0.25 mm (0.010 inches) and 1.50 mm (0.059 inches). As to the coil width, they come in sizes ranging from 1.5 mm (0.039 inches) and 15 mm (0.591 inches). However, designs can be highly customized if needed.

Finally, the three most common wire materials are Hastelloy, stainless steel (usually 300 series), and copper alloys. For use as a conductor or EMI/RF shielding, stainless steel is recommended. For applications that involve high heat and corrosive media, Hastelloy and Elgiloy may be recommended. Also keep in mind that these canted coil springs can be obtained with nickel, silver, or gold plating.

Used in a Wide Range of Industries and Applications

Canted coil springs are being used in a diverse group of industries and applications, including oil & gas, renewable energy, aerospace, defense, fluid power, transportation, semiconductor manufacturing, and medical devices

  • As a mechanical connector, canted coil springs are often used to lock together frame assembly of a ventilator cart or to hold components together in wind turbines.
  • As a multiple contact point conductor, canted coil spring assemblies are often used in active implantables such as pacemakers or neurotransmitters. 
  • As EMI/RF shielding, canted coil springs can be found in electrical enclosures or used with data transmission cables.
  • As a part of a spring energized seal, canted coil springs are used in critical aerospace applications and dangerous petrochemical environments involving extreme heat and corrosive materials.

Conclusion

FlexForce canted coil springs can be used as detent mechanisms, EMI/RF shields, multipoint electrical conductors, and energizing springs in seals. They are available in a number of options and can be fully customized to meet user needs. In addition, their reliable performance has already been proven in number industries and applications. If you are interested in FlexForce canted coil springs, contact us at Advanced EMC today.