Tech Talk Blog

Tivar HOT is a unique UHMW grade that has a dramatically higher continuous operating temperature (275F) than standard UHMW. Tivar HOT still has excellent wear and abrasion resistance, doesn’t absorb moisture, has excellent chemical resistance and meets FDA, USDA and 3A guidelines. We have found this product to be excellent for higher temperature zones in food processing and packaging equipment but it has also proven to be a great material in down-hole oil drilling applications!

Pretty diverse material. If you need excellent abrasion resistance, low friction, self lube bearing material with all of the other attributes mentioned, consider Tivar HOT from TriStar! And while you are looking around the site – stop by the Video Learning Center for some more information!

Fluoroloy H, aka Rulon  H, is an interesting combination of ceramics and PTFE. This unique dielectric material is used inside connectors for high power applications. The Fluoroloy H material has a slightly better dielectric constant compared to standard Teflon but has a higher rate of thermal conductivity.  This allows the heat being generated at the center conductor to transfer to the outer conductor more efficiently, which in turn increases the power level efficiencies of the connector. The thermal conductivity of Fluoroloy H is 1.21 W/m C and virgin Teflon PTFE is 0.24 W/m C. Fluoroloy H is easy to machine, similar to virgin or glass filled PTFE. Available in rod, sheet and tape.

For improved dielectric properties as well as heat sink properties, Fluoroloy H from TriStar Plastics is a  unique design option.

If you are interested, learn some more about Fluoropolymers or if you have a question that’s driving you crazy – Ask The Experts!

PCTFE has long been the go to material for valve seats, seals and gaskets used in cryogenic applications. But one thing that makes PCTFE unique is that it can be processed to meet a broad molecular state, i.e. crystalline or amorphous. PCTFE is a melt fluoropolymer and when molded in either sheet, rod or tube form it can be set at a specific crystalline state through a unique quenching process. This process is not as easily manipulated with extruded PCTFE rod so if you are looking for controlled molecular values you need to consider molded product.

As an example of some of the differences in physical properties between the amorphous PCTFE and crystalline PCTFE, consider these values:

Property                                            Amorphous                               Semi Crystalline                              Crystalline

% Crystallinity                                       40%                                                    55%                                               65%

Ultimate Tensile (psi)                      25,000                                           17,200                                              15,600

Elongation at Break (%)                        4                                                       2                                                         1.5

Tensile Modulus of Elast. (psi)   1,110,000                                           NA                                                 760,000

Compressive Strength   (psi)         34,000                                           37,500                                             38,000

Flexural Strength (psi)                    58,000                                            43,000                                              37,000

Flex Mod. Of Elast. (psi)               1,800,000                                     1,700,000                                    1,650,000

Crystalline/amorphous values are monitored by specific gravity and performance in cryogenic service utilizing amorphous grades of PCTFE has been well documented in terms of service life, sealability and property retention.

Ask The Experts at TriStar for more information on how PCTFE can be “custom tailored” to your application through molecular manipulation!

Polymer gears are common place in many industries and applications. The advantages of a polymer gear include noise reduction, self lubricating features, dramatic weight reduction and cost savings. From paper mill gears to drive gears in copiers, polymer gears have been successfully used for years. But, everything you know about metal gear design gets thrown out the door with polymers. There are many different factors that have to be considered when designing gears out of plastics including thermal expansion and contraction, physical strength, moisture absorption and possible chemical exposure.

Typical polymers for gears are cast nylons, injection molded nylons, polyester and acetal. Various fillers help to strengthen the base polymers such as glass and carbon fiber, aramid fibers and other additives are used to improve lubricity. More recently high end polymers like PEEK and Torlon have been used to make high temperature gears or gears where exceptional strength is required. No matter what the material, designing polymer gears will require some extra thought and a change from the norm. Tooth profiles and overall height may need to be changed to accomodate bending forces. Contact conditions at the root of the tooth may need modifications from the norm. Flex strength of the polymer will definitely come into play so input and output torque requirements will need to be reviewed closely.

While there are a lot of advantages to polymer gears you can’t overlook the basic differences of steel gears and polymer gears. Material choice and adherence to design changes required to address the physical, thermal and wear requirements of the gear must all be looked at closely. Tri Star has several thermoplastic and thermoset materials used frequently for gears and our engineering department can help you in this process. Have more questions? Ask The Experts – they are bound to know something. Or check out our Video Learning Center for a deeper look.

The first part of the answer is we need to know what kind of Teflon. DuPont’s family of Teflon products includes a number of different materials. PTFE is the best know of this family and the answer to your question for this material would be NO! PTFE does not hold up well at all in gamma radiation. As an example, 4Mrads of exposure reduces the tensile strength of the PTFE to 2% of it’s original value.

A better fluoropolymer for gamma irradiation would be DuPon’ts Tefzel product which is known by the chemical moniker of ETFE. In vacuum or air irradiation, Tefzel maintains a high level of physical integrity after long exposures.

Another fluoropolymer that does well in gamma is PCTFE, formerly known as Kel-F. PCTFE has minimal property loss even after doses of 16-18Mrads of exposure. Rates of property loss in all main categories are less than 30% which is quite good for fluoropolymers.

TriStar Plastics has more information on different methods of sterilization and how it affects most medical grade polymers. Ask The Experts – you’ll still like them when they’re angry (but they won’t be)!

Recent improvements in the pretreatment of certain fillers used in PTFE compounds has dramatically improved wear life. Carbon fibers are traditionally used for improving strength, heat transfer and electrical properties of PTFE. However, new chemical enhancements of the carbon fiber has resulted in dramatic tribological advances. By treating the fibers with plasma first, it prepares the surface for other chemical attachments. Experiments with nitric acid, amino silanes and two rare earth solutions showed varying degrees of improvement in both friction and wear. The best combination was plasma followed by a rare earth sol comprised of lanthanum oxide. This showed a reduction of dynamic friction to 0.054 and a K factor of 3.4, both exceptional numbers for a PTFE compound. New chemical modifications of fillers are being introduced which will lead to even more interesting new opportunities for seals, bearings and other dynamic application of PTFE compounds.

Take a look at our Video Learning Center for more information and our TriStar site.

High temperature polymers have been around for many years but industry is just now learning the value of these unique materials. Imidized materials like Celazole (PBI), Vespel and Meldin (PI) and Torlon (PAI) are able to maintain high physical strength in the 500-750F operating range. These materials have excellent wear properties and are available in many blends which enhance friction/wear properties, structural strength and thermal stability.

Sit back and learn a little more. Take a peek at our Video Learning Center.