Granular PTFE properties

Polytetrafluoroethylene selection. Polymer selection for compounding granular PTFE is relatively straightforward. Fine cut resins are used as a starting point to produce filled compounds. These powders have relatively small particle size and form the most uniform compounds. Typically, smaller particle size resins produce compounds with higher physical properties. 

Properties of granular PTFE compounds are presented in this section. A few points should be noted about filled PTFE compounds. Shape and size of the filler and resin particles, type of molding process, and processing conditions all influence the properties of parts made from compounds. Properties of compounds made with non-spherical particles are... 

These modified granular PTFE materials retain the exceptional chemical, thermal, antistick, and low-friction properties of conventional PTFE resin, hut offer some improvements ... 

Fine-cut granular resins resnlting from size redaction of the snspension polymer have a typical average particle size 20 pm to 40 pm. The small particle size of hne-cnt PTFE imparts the highest possible mechanical properties to articles made from grannlar resins. Fine-cnt resins (powders) have poor flow and low apparent density... 

The first PTFE that was made and sold commercially is known as granular polymer. The product mentioned above is isolated as a relatively coarse solid and the particles are reduced in size to the level desired. Thirty years ago standard product had a size about 500 micrmelting point of the polymer, and finally cooled. The molded products made in this manner often had up to several percent of voids that had a profound, deleterious effect on some properties of the material [25]. The solution was to ccxraninute the raw polymer to a particle size... 

As noted above, surface area is an important property for many micropowder applications. The only directly polymerized low MW PTFE available commercially is based on dispersion polymerization (high surface area) so either irradiated granular or thermally degraded PTFE is employed when a low surface area is preferred for the application. 

PTFE Fluoroplastic n Polytetrafluoroethylene is prepared by free radical polymerization of tetrafluor-oethylene in aqueous systems with persulphate or peroxide initiators to give granular or dispersion polymers. The polymers have exceptionally high thermal and thermo-oxidative stability and are completely solvent resistant. PTFEs are tough, relatively flexible materials which have outstandingly good electrical insulation properties as well as unusually low coefficients of friction. 

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