Tech Talk Blog

Tivar® HOT is a good alternative when standard UHMW is unable to withstand your operating temperature.  As the name implies, it is engineered to withstand high operating temperatures up to 220°F.  It is a diverse material that can be modified to fit a broad scope of applications.

Tivar HOT has near-zero water absorption, so it can be used in scalding and submerged applications.  It gives superior wear and chemical resistance, offers good impact strength, low friction, and is self-lubricating. It is also incredibly abrasion-resistant.

Tivar is a good solution for food processing and packaging equipment.  It meets FDA/USDA guidelines and is 3A Compliant.  We see it used in the production of sugar and candy.  Also many industrial applications such as pipe saddles, hopper liners, and conveyor guides.

It is available in sheet, rod or tube form, can be made to order, and is easily machined.  We can custom fabricate a part to match your print.

Torlon^® is a high-strength plastic, and is among the most expensive on the market. Torlon can be injection molded, compression molded, and extruded, and is ideally suited for severe service environments.  Applications include pump components, valve seats, bearings, rollers, high temperature insulators, electronic equipment, compressor components, and bearing cages.

The main characteristics of Torlon are a high maximum allowable service temperature, excellent mechanical strength and creep resistance over a wide range of temperatures, extremely low coefficient of linear thermal expansion, low flammability, exceptional resistance against high-energy radiation, moderate chemical and hydrolysis resistance, and excellent UV resistance.  And Torlon is excellent at maintaining physical properties.

We’ve got a range of Torlon grades available for your application:

● 4203 and 4503  – structural/insulating grade offering good insulating properties, low thermal expansion, moderate coefficient of friction

● 4301 and 4501 – extrusion most popular – gives excellent wear, reduced coefficient of friction, little to no stick slip, flex modulus over 1 million psi

● 4540 – bearing grade for extreme wear life – insulating materials (primarily structural): aluminum, and stainless steel

● 5530/4XG  – excellent electrical insulating properties, good wear resistance, abrasive towards mating surfaces, moderate dynamic coefficient of friction

● 4XCF  – another good bearing material in hi-temp applications, high stiffness,      lowest coefficient of thermal expansion of any standard polymer shape, non-abrasive

Tell us about your experience with Torlon.

Here’s a quick review of the different categories of plastics:

Plastics are classified into two categories:

1)      Thermoset – is any material that, once heated, cannot be reheated or reformed (Examples: Bakelite, Melamine, Teflon, Torlon, Celazole, glass epoxy systems, phenolic, Micarta

2)   Thermoplastic – any material that can be heated and reheated to make a finished part or stock shape (Examples: PVC, PEEK, polyethylene, nylon, acetal, acrylic)

Plastics also break down into two subcategories:

1)      Amorphous – Which is see-through or

2)      Crystalline – Not see-through.

The molecular structure is very important to the performance properties of any plastic material.

In processing, thermoset materials can only be compression or transfer molded. The process usually requires extremely high pressures and elevated temperatures. Thermoset materials usually require some form of reinforcement for stability and strength.

Thermoplastics can be extruded, injection molded, compression molded, blow molded, thermo formed, bonded to substrates, stamped and machined. And with thermoplastics, we have the ability to include additives to enhance properties like wear, fire resistance, electrical properties, and improvements in impact strength.  We can also reinforce with additives like glass fibers, carbon fibers, Kevlar, graphite, calcium carbonate.

We also classify by temperature:

1)      Commodity Plastics – lower cost and performance, typically doesn’t work above 200° F, good chemical resistance

2)      Engineering Plastics – 300° F limit, generally more versatile, used in structural and wear applications, available with enhancements

3)      High Performance Plastics -  most expensive, handle high temperatures over 300° F, associated with the most extreme operating conditions – thermally stable, excellent inherent wear properties, broad chemical resistance.

Our team is always looking at new alloys, new fillers, and extending chemistries to make new polymers.

Now that we’ve established the importance of bag selection in accelerated aging, let’s move on to temperatures.

The aging process subjects samples to elevated temperatures for specific periods of time to simulate the effects of real-time aging.  It is usually required in the testing of medical equipment such as diagnostic devices and surgical implements, and also in aerospace applications.

We’ve noticed the tendency for keeping testing temperatures too high.  By maintaining too high of a temperature, unintended physical changes such as melting may occur.  One must consider the most likely temperature extremes a device would see in practical use and test the device at that temperature.  Another temperature guideline is the Arrhenius reaction rate function, or “10-degree rule.”  This function states that a 10° C increase or decrease in the temperature of a homogenous process results in approximately a two times or ½ time change in the rate of a chemical reaction.

Share with us your experience with temperature testing.

Our team has seen a spike in interest in slipper seals.

Slipper seals, made from filled PTFE, are designed to act as a low friction interface between a static elastomer expander and the dynamic mating surfaces. i.e shaft or bore. With filled PTFE like our Ultraflon, slipper seals offer exceptional wear life, extrusion resistance, low friction and elimination of stick slip. Slipper seals can be used in both hydraulic and pneumatic applications, lubricated or dry and across a broad temperature range. Since these seals depend on the elastomer for their energizing function, the temperatures will depend on the operating capabilities of that elastomer.

PTFE slipper seals are made in a variety of geometries and cross sections to accommodate the design envelope. There are piston seals, rod seals, wiper seals and a variety of supporting components to make up a complete cylinder design. Tri Star has seal engineers on staff to assist in the design of your slipper seal requirements.

You know the drill – if you have a question, Ask The Experts!

Previous blog addressed importance of crystallinity control on PTFE as it relates to porosity, changes in physical strength and dielectric values. More Tri Star testing has shown better detail on the effects of processing and crystallinity. Specific gravity is the primary gage of crystalline or amorphous stages of polymers. In the case of PTFE the range is generally between 2.1 and 2.3 for unfilled resin. Testing showed that at 2.1 SpG the crystallinity of the molded product was approximately 38%. At 2.13 it was 47%, 2.15- 53%, 2.17 – 60%, 2.2 – 70%. Remember, the higher the crystallinity the lower the flex life, higher compressive stress, lower recovery, more permeability and lower wear life.

Another part of the equation has to do with microvoids as it relates to crystallinity. Microvoids are generally a result of poor attention to preforming conditions and to a lesser extent the sintering process. Microvoids, or porosity, have a direct bearing on crystallinity. As an example, a low microvoid material at 2.13 SpG would be 47% crystalline. However, if processing problems occur and void content grows you could see a substantial increase in crystallinity.  At a 1% microvoid level the 2.13 sample at 47% crystallinity would increase to 53%. Doesn’t sound like much but could have a great influence on the properties and wear of the material. Additionally, at 1% void content the dielectric strength of the PTFE would drop from it’s normal 500 v/mil to 320 v/mil. This is significant when considering PTFE as a dielectric insulator. For more information on the importance of quality in PTFE, contact Tri Star via this blog site or our website @www.tstar.com.

There is a lot of talk these days about biodegradable plastics, renewable resources, carbon footprints and the like. It’s interesting that as companies look at the feasibility of biodegradable plastics they also look at how it affects the other aspects of the ecology. If it takes more energy and produces more negative effects on nature we have to be able to justify the efforts. Today’s bioplastics technology is catagorized several ways. There are pure bio polymers that are based on polylactides (fermented bacteria), cellulose ( naturally occuring wood product), lignin (a macromolecular by-product of paper), biopolymer blends (combination of bio sources) and finally polymer blends which utilize biomaterials and petroleum products.

Bioplastic products are further classified by either compostable or true biodegradable. Compostable bioplastics degrade by at least 90% within 6 months by natural environmental conditions; i.e. temperature, humidity and pH. This degradation occurs through typical composting breakdowns and the result is by-products such as water, carbon dioxide, methane and humus.  Some biodegradable polymers will break down through naturally occuring micro-organisms such as bacteria or fungi. Today, most of the bioplastics that fall into this category are packaging films and consumables but that is changing. More and more bioplastics are being developed with higher engineering potential. Materials that can withstand loads, can be extruded into shapes and molded or machined into finished parts for things as diverse as musical instruments to display panels in store fronts. It is also available in stock shapes such as rod, sheet, tube and custom profiles. Tri Star Plastics is working closely with bio-partners to develop more and more options in this interesting new world of bio-plastics. For more information on this technology, contact our Technical Department at www.tstar.com or send us a return blog! More interesting things on the way!

Recent headlines tell us that everything from our kitchen cutting boards, Tupperware and soda fountain delivery tubing are infected with everything from fecal matter to salmonella. There are solutions available thanks to new polymer technology using antimicrobial additives and surface treatments. Many polymers are now available with silver ions which help to effectively inhibit the potential growth of bacteria, yeast and fungi on the polymer surface. By using unique zeolite carriers with silver ions, a counter force to the sodium ions present in moisture  interrupt respiration, reproduction and metabolism of destructive microbes. TriStar offers several polymer solutions now in molding and extrusion resins to dramatically reduce the potential of microbial growth in your products. Browse through our Video Learning Center for even more information.

The growth of plastics in medical devices is growing exponentially around the world.  Plastics are regulated like any other materials that may come in contact with human tissue or fluids and that usually falls under testing procedures issued under USP or ISO10993. There are three time scales for biocompatible devices. “Limited” would be less than 24 hour exposure, “Prolonged” is 24 hours to 30 days and “Permanent” is 30 days and longer. Device’s are categorized as Surface Devices which would be items such as electrodes for monitoring, contact lenses, catheters, endotracheal tubes, sigmoidoscopes and similar devices. Second would be Externally Communicating Devices such as  laprascopes, blood administration devices, pacemakers, oxygenators and the like. Finally are Implant Devices such as orthopedic pins or plates, heart valves, grafts, stents and similar devices.

Testing of these devices includes mechanical, thermal, chemical tests as well as systemic injection, intracutaneous and implantation. All of these must be done before a plastic component can be approved. Typical materials for biocompatible applications include medical grades of PVC and Polyethylene, PEEK, Polycarbonate, Ultem PEI, Polysulfone, Polypropylene and Polyurethane. For more specific information on Biocompatible materials as well as special plasma preparation treatments of all of these materials, contact TriStar Plastics at www.tstar.com and visit our Video Learning Center and our Materials Database.

Torlon PAI from Solvay is one of the outstanding polymers for high temperature applications. Torlon is available in various forms and with different enhancements to meet diverse applications such as bearings, dielectric insulators and structural components. Torlon’s physical properties maintain very high values even at the maximum operating temperatures.

You can learn more in our Video Learning Center, too!