Fluoropolymers fillers

Graphite Filler - A crystalline form of carbon in powder form. Graphite occurs naturally and also is produced by heating petroleum coke, carbon black, and organic materials. Used as a lubricating filler for nylons and fluoropolymers. Also... 

Since the density of plastics highly depends on the presence of fillers or other additives, this property is far from being a characteristic feature. Unfilled polyolefines (polyethylene and polypropylene), a number of elastomers (natural rubber and silicone rubber), and foamed plastics come within the rare category of polymers which float on water. Some fluoropolymers exhibit a density around or greater than 2 g/cvo (see also Table 3.3). 

Normal Thermoplastics (except fluoropolymers) without fillers or flame retardants Satisfactory Good Good Excellent... 

Nonetheless, it can be seen that a range of fillers and polymeric matrices were studied and different ways were used for the production of composite bipolar plates. Graphite and carbon black as fillers are to be found in nearly every study, and accordingly, some polymers are preferred to be used for composite bipolar plates. The reasons for both the fillers and the matrices are obvious. Graphite and carbon black have outstanding chemical stability against corrosion when compared with metallic fillers they achieve an adequate conductivity and are obtainable at a reasonable price. In case of the matrices the chemical corrosion resistance is also a main criterion, and polyolefin materials, fluoropolymers, polyphenylene sulfide (PPS), and phenolic resins are particularly favored. 

Fluoropolymer-based additives are very useful, offering low temperature processability, chemical resistance, weatherability, self-extinguishing, and flexibility. Available as powders, pellets, dispersions or master batch concentrate (at additions of 250-1000 ppm), they are designed for use in PO film extrusion to eliminate melt fracture or problems arising from die build-up when running PO polymer with fillers and pigments [17, 59]. 

Fluoropolymers have outstanding chemical resistance, low coefficient of friction, low dielectric constant, high purity, and broad use temperatures. Most of these properties are enhanced with an increase in the fluorine content of the polymers. For example, polytetrafluoroethylene, which contains four fluorine atoms per repeat unit, has superior properties compared to polyvinylidene fluoride, which has two fluorine atoms for each repeat unit. Generally, these plastics are mechanically weaker than engineering polymers. Their relatively low values of tensile strength, deformation under load or creep, and wear rate require the use of fillers and special design strategies. 

Organic Filler - Organic fillers are made from natural or synthetic organic materials. Natural material derived organic fillers include wood and shell flours. Synthetic material derived fillers include fluoropolymer spheres and milled polymer waste. Organic fillers are characterized by relatively low cost and low density. They might increase the flammability and decrease the moisture resistance of plastics. See also Mineral Filler. 

FIGURE 13.9 Effect of various fillers on the wear rate of Nylon 6,6. (Adapted from Lubricomp Internally lubricated reinforced thermoplastics and fluoropolymer composites, LNP Bulletin, 254-691.)... 

There are two main lines of work here one is improving the tribological properties of specific polymers. Blending with fluoropolymer [4], addition of inorganic filler [5 - 6] and y-radiating the surface [7] have been used to migitage wear and to lower friction. Another is the improved understanding of wear mechanisms in polymers. 

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