Specialty polymers and their blends

The specialty resins are expensive, produced in relatively small volumes either for a specific application or looking for a market niche. Their Tg 200 °C and modulus 3 GPa. In 1991 the total world consumption of polysulfones (PSF) and polyethersulfones (PES) was 8.5 kt. Blends of the following polymers are known polyfiuorocarbons, polysiloxanes, sulfur-containing polymers (PPS, PPSS, PES, and PSF), polyetherketones (PEK, PEEK, PEKK), polyimides (PI, PEI, and PAI), PAr, COPO, polyphosphazene (PHZ), and LCP. 

Known in Germany since 1933, polytetrafluoro-ethylene (PTEE) is a semicrystalline resin (92-98% crystallinity), with T = 342°C and melt viscosity of 7 - 10 GPas. Others, more common fluoro-polymers are polychlorotrifluoroethylene (PCTFE), Hostaflon commercialized in 1934, fluorinated ethylene-propylene (FEP), Teflon -FEP introduced in 1972, and numerous copolymers with Tjjj = 260 to 304°C, processable at = 315 to 425°C, and having the degradation temperature, deg 440°C. The fluoropolymers are 

In blends, fluoropolymers are used in small quantities to enhance throughput, reduce the frictional properties and increase the wear resistance. Blends comprising 0.3-50 wt% of a low molecular weight PTFE (T 350°C) with engineering resin showed improved anti-friction properties [Asai et al, 1991]. 

PPS and PEEK blended with a fluoro(co)-polymers and reinforced with either CF or GF were wear resistant with a short break-in period for forming a self lubricating film [Davies and Hatton, 1994]. Many commercial blends contain fluoropolymers (primarily PTFE) for the improved weatherability, wear and solvent resistance SUPEC — self-lubricating blend of crystalline PPS with PTFE and 30 wt% GF, Lubricomp blends from LNP and similar/JTP blends from RTP Co. (e.g., 15 wt% PTFE, 30 wt% GF and any of the following resins ABS, PA, PEST, PC, PE, PEI, POM, PP, PPE, PPS, PS, PSF, PVDF, SAN, TPU, PEEK, PES, etc.), Sumiploy from Sumitomo Chem. Co., etc. [Utracki, 1994]. 

Polysiloxanes, [-O-Si(RR )-], are linear resins that can be branched or crosslinked into elastomers. They have high compressibility, permeability to gases, low T and viscosity, exceptional weather-ability, low surface tension coefficient and are relatively expensive. Siloxane polymers or copolymers have been incorporated into engineering or specialty resins to improve processability, toughness, HDT, solvent and weather resistance. 

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