Uncategorized

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.

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.

Hytrel (property of the Dupont Company) is gaining in popularity as a material for seals, and there a number of reasons for this. In this blog post, we are going to talk about the general characteristics of Hytrel as well as the specific grades used for sealing applications.

What is Hytrel?

Hytrel is a TPC-ET thermoplastic polyester elastomer made by Dupont. Hytrel can be found in applications that seem to vary significantly in requirements and environmental challenges, such as off-road transportation equipment, oil and gas, hydraulic power, food handling, and medical devices. It is also used in electronics, automobiles, healthcare equipment, power tools, sporting goods, appliances, and cables.

Characteristics of Hytrel

Hytrel has a long list of excellent characteristics, including impact resistance, toughness, and resistance to chemical attack (including hydrocarbon solvents and fuels). In terms of sealing applicants, it offers:

• Flex fatigue resistance
• Spring-like properties
• Creep resistance
• Inherent flexibility
• The ability to flex in multiple directions
• Wide operating temperature range (cryogenic to +315°F)

In addition, Hytrel retains mechanical properties even at high temperatures and remains flexible at low temperatures. Hytrel also lends itself to a variety of manufacturing methods, including extrusion, blow molding, injection molding, and rotational molding. However, it is sensitive to water and phosphate fluids above 175°F.

Grades and Blends of Hytrel

Hytrel is available in various grades and blends, including seven specific grades that are well-adapted for seals. In addition to the grades discussed below, there are also renewable sourced options. Note that stabilizing additives can be combined with these grades to improve Hytrel’s resistance to heat aging and UV light.

Hytrel 4056

Hytrel 4056 is the most flexible grade, offering both toughness and strength over a considerably wide temperature range. It works extremely well for low-temperature applications because of its ability to retain flexibility. In addition, its low modulus allows it to be formed using extrusion and has a low melting point.

Hytrel 4068 and Hytrel 4069

Both Hytrel 4068 and 4069 provide flex-fatigue and creep resistance along with outstanding low-temperature properties. These grades can be formed using molding or extrusion and possess a higher melting point than Hytrel 4056 and a lower modulus. In addition, there is a food-grade available: Hytrel 4068FG.

Hytrel 4556

Hytrel 4556 is very similar to 4068 and 4069, with a low-to-medium modulus and can be manufactured using both extrusion and molding. This grade works extremely well for seals and gaskets.

Hytrel 5526 and Hytrel 5556

In terms of general properties, Hytrel 5526 provides a good balance. Its flow properties, however, primarily limit it to injection molding. Hytrel 5556 also offers a balance of properties with a medium modulus. It works well with extrusion but does not have the same high-flow properties available with Hytrel 5526. 

Hytrel 6356

Hytrel 6356 offers an excellent balance of properties such as toughness, flexibility strength, thermal resistance, and creep resistance. This high modulus grade is well adapted both to molding and extrusion processes.

Hytrel 4053FG NC010

When food contact grade seals are needed, Hytrel 4053FG NC010 may be an option. This is a low modulus extrusion grade whose properties include creep resistance, good low-temperature properties, and flex-fatigue resistance. 

Hytrel 5553FG NC010

This is a medium modulus molding and extrusion grade of Hytrel that provides a good balance of properties. It is intended for applications involving food contact.

Hytrel 6359FG NC010

Another good grade option of Hytrel, this material provides a good balance of properties including strength, toughness, flexibility, creep resistance, and thermal resistance. It is a medium to high modulus grade that works well with both molding and extrusion processes.

Benefits of Using Hytrel

When used in sealing applications, Hytrel offers a number of distinct benefits. For example, Hytrel can be used to replace multi-piece assemblies (including those composed of various materials) with a single component.

Because Hytrel has excellent creep and recovery properties, seals using Hytrel will be more resistant to dimensional changes and less likely to be permanently deformed. This is critical in many sealing applications, including those where there are extreme pressure and temperature changes. And because it can flex in multiple directions for far more cycles than a traditional elastomer such as rubber.

Unlike some seal materials, Hytrel grades vary according to modulus, which makes Hytrel a very versatile material choice. The differences in modulus are important: low modulus options can be used where little force should be needed to stretch the material, while high modulus grades work well for situations where significant force should be required to result in stretching. In addition, Hytrel is available in Shore D hardness ranging from 30 to 82.

As mentioned earlier, Hytrel has excellent properties when it comes to chemical compatibility and resistance to chemical attack. More specifically, it is resistant to mineral oils, greases, water-based hydraulic fluids, dilute acids, dilute bases, glycol, and hydrocarbon fuels. There are also grades of Hytrel that offer excellent resistance to the degrading effects of radiation. 

Hytrel is available in food grades that conform to both FDA and  European Food Contact regulations.  There are also grades in compliance with regulatory requirements that make them suitable for use in medical devices and other healthcare applications.

Conclusion

Hytrel combines the strength of engineering plastics with the flexibility of elastomers and the ease of processing provided by thermoplastics. Its combination of properties and flexibility in terms of manufacturing processes make it an excellent option for sealing applications

Today more and more countries are entering the space industry. According to the Space Foundation, the global market for space exploration was a whopping $383.5 billion worldwide in 2017, with a 100% increase in the total number of spacecrafts deployed. It is expected to grow to $1.1 trillion by 2040.

As the space market opens up, so does the need for technology that assists with cost, sustainability, efficiency and safety- such as seals.

In fact, polymer seals have been used in a variety of functions for spacecrafts such as:

• Propulsion
• Payload Systems
• Ground Support Equipment
• Regulators
• Main Fuel and Oxygen Valves
• Regulators
• And more!

In today’s blog post, we will explore the use of polymer seals in the space industry.

A Changing Landscape

Since the first expedition into space in 1961 by Russian cosmonaut Yuri Gagarin, there has been a surge in emerging countries and private sectors entering the space race.

In 2002 Elon Musk founded SpaceX, a private company whose goal is to manufacture and launch advanced rockets and spacecrafts with the goal of enabling commercial trips into space. In 2010 it became the first private company to return a spacecraft from low Earth orbit in 2010 and the first commercial spacecraft to deliver cargo to and from the International Space Station in 2012.

In India, the Indian Space Research Organization (or ISRO) has developed a massive and ambitious space program. In 2014 they launched their Mars orbiter, becoming the fourth space agency and the first in Asia to reach the red planet. In 2017, it launched 104 satellites in a single rocket, tripling Russia’s record.

With so many new players entering the scene, the space industry has never looked more exciting. This also requires an increase in demand for high quality parts, such as polymer seals.

Space is Cold and Engines are Hot

Polymer spring energized seals are commonly used in a variety of space applications because of their durability and ability to withstand extreme temperatures.

With temperatures in space reaching cryogenic (-238*F or -150*C) it is important that the seals used can withstand the extreme temperatures. The outer polymer lip of a spring energized seal for example allows the seal to be used in temperatures of -423*F (-253*C) to 302*F (150*C).

On top of having seals that can be used in the cold, dark vacuum of space, seals are also used in conjunction with things like thrusters, combustion chambers, and other parts of the shuttle where temperatures can reach a whopping 6,000*F (3,315*C).

Aggressive Chemicals

Many seals face frequent exposure to liquid oxygen and liquid hydrogen, the latter of which must be below 20K (-423*F or -253*C) in order to reach a liquid state. This puts an incredible amount of strain on the seal. One way around this is to make seals out of high-quality polymers such as PTFE, Torlon and more.

Increase of Pressure

In outer space, the pressure is 1.322 x 10^-11 Pa. For those keeping track at home, this is essentially zero. However, the act of leaving the Earth’s atmosphere causes such a huge fluctuation in pressure that there is a potential for metal and other hardware to open, which in tern could potentially impact the seal.

As such it is critical that seals used can hold up to the extreme fluctuation of pressure, and continue to run, to keep the shuttle and its crew safe.

Teflon, or PTFE, is a popular material used because of its ability to not only handle extreme temperatures, but extreme pressure fluctuations as well.

Cost Efficiency

As of 2012 it is estimated that the average launch cost of a NASA space shuttle is around $576 million. That cost does not factor in the price to build the craft, which values at a whopping $3.5 billion. As such, it behooves space programs to find ways to not only be cost efficient, but to be sustainable as well.

Luckily, with seals, making them out of polymer materials solves both problems!

Because of it’s ability to be produced at high volumes, making seals out of polymers can greatly reduce overhead cost. And because the plastic can be melted down and reused, they are highly sustainable as well!

In Conclusion

With more and more people interested in space exploration, it is becoming more and more critical to have high quality parts to perform critical functions.

Polymer seals are the best choice for companies looking to have a high quality, cost efficient, and sustainable part that will withstand the rigors of space travel.

For more information, or to learn how Advanced EMC Technologies can help your spaceship blast off, contact us today!