Engineering thermoplasts

ABS systems [ACRYLONITHILE POLYTffiRS - ABS RESINS] (Vol 1) Engineering thermoplastics... 

The recycling of engineering thermoplastics such as polyamides, ABS, and PTEE have been discussed (50). Property degradation as a result of use, recovery, and recycling is a concern. 

Like most other engineering thermoplastics, acetal resins are susceptible to photooxidation by oxidative radical chain reactions. Carbon—hydrogen bonds in the methylene groups are principal sites for initial attack. Photooxidative degradation is typically first manifested as chalking on the surfaces of parts. 

Although ABS resins have a long history by industry standards, the products are anything but mature. ABS resins and blends are, and are expected to remain, the engineering thermoplastics of choice for a wide array of markets. 

Ethylenebis(tetrabromophthalimide). The additive ethylenebis(tetrabromophthalimide) [41291 -34-3] is prepared from ethylenediamine and tetrabromophthabc anhydride [632-79-1]. It is a specialty product used ia a variety of appHcations. It is used ia engineering thermoplastics and polyolefins because of its thermal stabiUty and resistance to bloom (42). It is used ia styrenic resias because of its uv stabiUty (43). This flame retardant has been shown to be more effective on a contained bromine basis than other brominated flame retardants ia polyolefins (10). 

Triphenyl phosphate [115-86-6] C gH O P, is a colorless soHd, mp 48—49°C, usually produced in the form of flakes or shipped in heated vessels as a hquid. An early appHcation was as a flame retardant for cellulose acetate safety film. It is also used in cellulose nitrate, various coatings, triacetate film and sheet, and rigid urethane foam. It has been used as a flame-retardant additive for engineering thermoplastics such as polyphenylene oxide—high impact polystyrene and ABS—polycarbonate blends. 

The typical mechanical properties that qualify PCTFE as a unique engineering thermoplastic are provided ia Table 1 the cryogenic mechanical properties are recorded ia Table 2. Other unique aspects of PCTFE are resistance to cold flow due to high compressive strength, and low coefficient of thermal expansion over a wide temperature range. 

Styrene—maleic anhydride copolymer [9011-13-6] engineering thermoplastics, paper treatment chemicals, floor poHshes, emulsifiers, protective coUoids, antisoil agents, dispersants... 

Aromatic polyethers are best characterized by their thermal and chemical stabiUties and mechanical properties. The aromatic portion of the polyether contributes to the thermal stabiUty and mechanical properties, and the ether fiinctionahty faciUtates processing but stiU possesses both oxidative and thermal stabiUty. With these characteristic properties as well as the abiUty to be processed as mol ding materials, many of the aromatic polyethers can be classified as engineering thermoplastics (see Engineering PLASTICS). 

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

Noryl is a rigid dimensionally stable material. Dimensional stabiUty results from a combination of low mold shrinkage, low coefficient of thermal expansion (5.9 x 10 per° C), good creep resistance (0.6—0.8% in 300 h at 13.8 MPa (2000 psi)), and the lowest water absorption rate of any of the engineering thermoplastics (0.07% in 24 h at room temperature). Noryl resins are completely stable to hydrolysis. They are not affected by aqueous acids or bases and have good resistance to some organic solvents, but they are attacked by aromatic or chlorinated aUphatic compounds. 

The effect of temperature on PSF tensile stress—strain behavior is depicted in Figure 4. The resin continues to exhibit useful mechanical properties at temperatures up to 160°C under prolonged or repeated thermal exposure. PES and PPSF extend this temperature limit to about 180°C. The dependence of flexural moduli on temperature for polysulfones is shown in Figure 5 with comparison to other engineering thermoplastics. 

Alkylated phenol derivatives are used as raw materials for the production of resins, novolaks (alcohol-soluble resins of the phenol—formaldehyde type), herbicides, insecticides, antioxidants, and other chemicals. The synthesis of 2,6-xylenol [576-26-1] h.a.s become commercially important since PPO resin, poly(2,6-dimethyl phenylene oxide), an engineering thermoplastic, was developed (114,115). The demand for (9-cresol and 2,6-xylenol (2,6-dimethylphenol) increased further in the 1980s along with the growing use of epoxy cresol novolak (ECN) in the electronics industries and poly(phenylene ether) resin in the automobile industries. The ECN is derived from o-cresol, and poly(phenylene ether) resin is derived from 2,6-xylenol. 

The largest use for 2,4-dicumylphenol is in a production of a uv stabilizer of the benzotriazole class, 2-(2 -hydroxy-3, 5 -dicumylphenyl)benzotriazole [70321-86-7] which is used in engineering thermoplastics where high molding temperatures are encountered (67). The high molecular weight of... 

Uses. A principal use of thionyl chloride is in the conversion of acids to acid chlorides, which are employed in many syntheses of herbicides (qv), surfactants (qv), dmgs, vitamins (qv), and dyestuffs. Possible larger-scale appHcations are in the preparation of engineering thermoplastics of the polyarylate type made from iso- and terephthaloyl chlorides, which can be made from the corresponding acids plus thionyl chloride (186) (see Engineering plastics). 

An example of a sulfite ester made from thionyl chloride is the commercial iasecticide endosulfan [115-29-7]. A stepwise reaction of thionyl chloride with two different alcohols yields the commercial miticide, propaigite [2312-35-8] (189). Thionyl chloride also has appHcations as a co-reactant ia sulfonations and chlorosulfonations. A patent describes the use of thionyl chloride ia the preparation of a key iatermediate, bis(4-chlorophenyl) sulfone [80-07-9] which is used to make a commercial polysulfone engineering thermoplastic (see Polymers CONTAINING SULFUR, POLYSULFONe) (190). The sulfone group is derived from chlorosulfonic acid the thionyl chloride may be considered a co-reactant which removes water (see Sulfolanes and sulfones). 

The Hquid monomers are suitable for bulk polymerization processes. The reaction can be conducted in a mold (casting, reaction injection mol ding), continuously on a conveyor (block and panel foam production), or in an extmder (thermoplastic polyurethane elastomers and engineering thermoplastics). Also, spraying of the monomers onto the surface of suitable substrates provides insulation barriers or cross-linked coatings. 

Polyurethane engineering thermoplastics are also manufactured from MDI and short-chain glycols (49). These polymers were introduced by Upjohn/Dow under the trade name Isoplast. The glycols used are 1,6-hexanediol and cyclohexanedimethanol. 1,4-Butanediol is too volatile at the high processing temperatures used in the reaction extmsion process. Blends of engineering thermoplastics with TPU are also finding uses in many appHcations... 

Injection-Molded Products. Numerous housings, electrical enclosures, and cabinets are injection-molded from rigid PVC. These take advantage of PVC s outstanding UL flammabiUty ratings and easy mol ding into thin-waHed parts. PVC has developed melt flow capabiUties to the point where it competes with essentially any other flame-retarded engineering thermoplastic and molds easier than most. 

The use of elastomeric modifiers for toughening thermoset resias generally results ia lowering the glass transition temperature, modulus, and strength of the modified system. More recendy, ductile engineering thermoplastics and functional thermoplastic oligomers have been used as modifiers for epoxy matrix resias and other thermosets (12). 

Extmded engineering thermoplastic stock can be treated like other building material ia that it can be machined, cut, and fastened. However, none of the engineering plastics can be considered a one-for-one substitute for metals or wood. For example, impact resistance must be considered, and glues, paints, etc, must be screened for chemical aggressiveness and adhesion capabiUty. 

Engineering thermoplastics have also been used ia preimpregaated coastmctioas. The thermoplastic is thoroughly dispersed as a coatiauous phase ia glass, other resias, carboa fibers (qv), or other reinforcement. Articles can be produced from these constmctions usiag thermoforming techaiques. For example, the aerospace iadustry uses polyetheretherketoae (PEEK) ia wovea carboa-fiber tapes (26). Experimental uses of other composite coastmctioas have beea reported (27) (see also Composite materials, polymer-matrix). 

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