Tech Talk Blog

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.

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Molecular weight and crystallinity are two factors in PTFE that determine many of it’s performance qualities. Both of these properties are highly dependant on the sintering operation of the PTFE production. If the material is cooked (sintered) too long or at too high a temperature it can degrade the polymer. Molecular weight is a measure of the polymer chain length and it affects flex life, tensile strength and elongation. As molecular weight increases so do these properties and paying attention to gel temperatures and dwell times during sintering is extra critical.

Crystallinity of PTFE can vary considerably depending on processing. This value can be seen in small variations in the specific gravity although in practice most PTFE materials fall in the 50-60 percent crystalline percentage. Increasing crystallinity decreases flex life, increases compressive stress and decreases recovery values, permeability and wear life. Other properties of PTFE, such as thermal, chemical, electrical and friction, are not generally affected by crystallinity changes.

So, sintering and other processing steps do a make a difference in deterimining the quality of PTFE. If you need to maximize the performance of your PTFE parts, including Rulon, Fluorosint, Ultraflon or even generic products, be sure you contact Tri Star Plastics first.  We can help you select the right material and the right process.

New TriSteel PE material utilizes the outstanding wear properties of PEEK, combined with the PTFE low friction additive, make this product unique in thin wall metal backed products. The PEEK liner has excellent resistance to chemicals and when combined with a stainless steel shell material it is perfect for applications in chemical pumps, valves or environments where temperature is critical. TriStar’s TriSteel PE bearing is available in inch and metric sizes as sleeve, flange and thrust bearings. Ask the Experts or visit www.tstar.com for more information.

Composite self lubricating bearings take advantage of superior strength from filament or laminate wound structure. Add to that a variety of lubricating media like PTFE, MOS2, Graphite and combine with abrasion resistant, high strength woven liners and you have the makings of super bearings! Composite bearings are primarily applied to high load, low speed applications however new liner materials allow for speeds up to 500 feet per minute without lubrication. Another unique quality of composite bearings is they love to be under water. Excellent materials for marine applications under water, deck side and dock side.

Check out some stories in our Shooting Star Archives and look on www.tstar.com for more information!