High temperature-resistant thermoplastics

PEEK is a high-temperature-resistant thermoplastic suitable for wire coating, injection molding, film and advanced structural composite fabrication. The wholly aromatic structure of PEEK contributes to its high-temperature performance. 

For the behavior of high temperature-resistant thermoplastics see Section 6.2.19. 

Conductive reinforcements in thermoplastics are a new application of composites [2891. High temperature resistant thermoplastics, such as PPS, PEI, PPO and liquid crystal polyesters, have been combined with conductive fibers, generally chopped graphite and nickel coated graphite. Fiber distribution, orientation and fracture morphology were determined by optical and SEM techniques. Poor bonding in the nickel coated graphite composite, as observed in SEM tensile fractures, resulted in lowered tensile and impact properties. 

Figure 19.4a shows examples for thermogra-vimetric analysis (TGA) analysis for state-of-the-art HT-PEM plates of type BPP4 and low temperature LT-PEM materials as a reference. Recently developed HT-PEM materials with high temperature resistant thermoplastic binder polymers (PPS and PSU Ultrason ) are shown in Fig. 19.4b. 

Potente, H., Michel, R, and Heil, M., Infrared Radiation Welding A Method for Welding High Temperature Resistant Thermoplastics, ANTEC Conf. Proc., Soc. Plastics Eng., 1991. 

Polyester. Poly(ethylene terephthalate) [25038-59-9] (PET) polyester film has intermediate gas- and water- vapor barrier properties, very high tensile and impact strengths, and high temperature resistance (see Polyesters, thermoplastic). AppHcations include use as an outer web in laminations to protect aluminum foil. It is coated with PVDC to function as the flat or sealing web for vacuum/gas flush packaged processed meat, cheese, or fresh pasta. 

The thermoplastic fiber is tough, with relatively high temperature resistance. It can be processed into yams that maintain their properties at elevated environmental temperatures, e.g. in tire reinforcement or for permanent-press fabrics. 

Poly(butylene terephthalate) (PBT) is a semicrystalline, thermoplastic polyester which is completely analogous to PET except that it has a longer, more flexible butylene chain linkage which imparts a rapid crystallization rate, thus making PBT well suited to injection moulding processes. This polyester is used widely for electrical and electronic components due to its high temperature resistance and good electrical properties (Chapter 8). 

For many years prior to the development of high-temperature thermoplastics and thermosets, such as the polyimides. polysulfones, and epoxies, phenolic molding material dominated the high temperature-resistant market. This emphasizes their ability to resist temperature degradation in the 400-500°F (204-260 C) range. Because phenolics were found to possess excellent ablative properties, it has been reported that both the American and Soviet space efforts used them in combination with certain other... 

PT, 5-phenyltetrazole. Efficient, decomposes at 460°-480°F (238°-249°C). Decomposition gases are almost all nitrogen. Used with ABS, nylon, PC, thermoplastic polyester, and other high-temperature resistant plastics. 

Another (family of linear aromatic polymers is the polysulfones. They are tough, high-temperature-resistant engineering thermoplastics. Polysulfones may be synthesized by the nucleophihc substitution of alkali salts of biphenates with activated aromatic dihalides. A typical example is the preparation of bisphenol A polysulfone (21) from the reaction of disodium salt of bisphenol A with dichlorodiphenyl sulfone ... 

Polyacetal polyphenylene oxide are widely used as engineering thermoplastics, and epoxy resins are used in adhesive and casting application. The main uses of poly(ethylene oxide) and poly(propylene oxide) are as macroglycols in the production of polyurethanes. Polysulfone is one of the high-temperature-resistant engineering plastics. 

Thermosets are hard. They are cross-linked with a narrow mesh in all directions. They are impervious to plastic deformation, infusible, and highly temperature resistant. Because thermosets are densely cross-linked, they are impossible to dissolve and quite difficult to swell. They are hard and brittle at room temperature. Electrical socket-outlets are manufactured from thermosets, for example, because resistance to high and low temperatures is very important here. Thermoplastics are incapable of meeting these requirements. 

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