Thermoplastic polyesters development

Today about 75% of the market is held by General Electric and Bayer with their products Lexan and Makrolon respectively. Other manufacturers are ANIC (Italy), Taijin Chemical Co., Mitsubishi Edogawa and Idemitsu Kasei in Japan and, since 1985, Dow (USA) and Policarbonatos do Brasil (Brazil). Whilst this market is dominated by bis-phenol A polycarbonates, recent important developments include alloys with other thermoplastics, polyester carbonates and silicone-polycarbonate block copolymers. 

Thermoplastic polyester elastomers such as the Du Pont product Hytrel were developed later than the polyurethane materials, being first introduced in 1972. They have similar characteristics to the polyurethanes but there is an upward shift in the hardness range (i.e. the softest grades are not so soft, but the hardest grades are harder than the corresponding extreme grades in the polyurethanes). 

In terms of volume and economic importance, thermoplastic polyesters are dominated by PET, which has experienced a tremendous development in fibers and... 

The primary crystalline polymer based on CHDM is the terephthalate, poly(1,4-cyclohexylenedimethylene terephthalate) (PCT). This polyester was originally developed for fiber applications but has since found wider utility as a reinforced polymer for injection molding and (when copolymerized with a small amount of isophthalic acid) as a material for crystallized food packaging trays. The key property of PCT which sets it apart from other thermoplastic polyesters in these latter applications is its melting point. 

Solid-state polycondensation of thermoplastic polyesters such as PET is therefore both time-consuming and energy-intensive. Recently, additives have been developed to accelerate this process [23, 24], Such additives enable PET with a very high IV to be produced at reduced residence times in the solid-state reactor, with enhanced outputs and at a reduced cost. Such additives accelerate the IV enhancement of PET at low cost. One such SSP accelerator is Irgamod 1425 which when used in PET at levels of between 0.1-0.5wt% gives an SSP acceleration of approximately 50 % (see Figure 14.5). 

Mat and continuous glass fibre reinforcements theoretically all the thermoplastics are usable in these forms, but up to now developments have concentrated on polypropylenes (PP), polyamides (PA) and thermoplastic polyesters (PET) fibre-reinforced PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. 

From the beginning, poly(ester-imide)s had been developed as thermo-setting polymers. In the 1970s a development was started to use imide modification for improving the properties of thermoplastic polyesters. Later on in the patent literature liquid crystalline polymers can be found as being claimed as molding resins. 

During the past three decades a few groups of materials have been developed that could be considered as being in this category. Designated as thermoplastic elastomers, they include (1) styrene-diene-styrene triblock copolymers (2) thermoplastic polyester elastomers and thermoplastic polyurethane elastomers and (3) thermoplastic polyolefin rubbers (polyolefin blends). 

Following the initiative of Wiley-VCH, this project has been started with the target of offering an idea about the recent rapid development of biodegradable polyesters and thus to widen the general picture of thermoplastic polyesters. As a matter of fact, the present book can be considered as volume 3 of the above mentioned Handbook. ... 

Thermoplastic polyester resin can be solvent cemented using hexafluoroisopropanol or hexafluoroacetone sesquihydrate. The solvent should be applied to both surfaces and the parts assembled as quickly as possible. Moderate pressure should be applied as soon as the parts are assembled. Pressure should be maintained for at least one to 2 min maximum bond strength will not develop until at least 18 hr at room temperature. Bond strengths of thermoplastic polyester bonded to itself wiU be in the 800 to 1500 psi range. 

In thermoplastics, carbon fiber compounds have been developed with nylon, polysulfone, thermoplastic, polyester, polyphenylene sulfide, polycarbonate, polypropylene, polyamide-imide, and ethylene/tetrafluoroethylene copolymer. Carbon fiber-reinforced molding compounds are available with carbon fiber contents of various levels such as 20, 30, and 40 weight percent. Nylon 66 molding compounds have also been developed with hybrid combinations of carbon and glass fiber reinforcements. 

Recently, impact modifiers have been developed for plastics other than PVC. Polybutylene and other olefinic thermoplastic elastomers, for example, are being used to enhance the processability, toughness, and heat stability of polypropylene film. Hydroxy-terminated polyethers are being used to increase the impact resistance of polystyrene. Other conunon applications are polycarbonate, polyurethane, thermoplastic polyester, epoxy, and polysulfone. 

Renewed development and marketing effort is expected with brominated epoxy oligomers, now in the hands of Resolution Performance Products, following a sell-off from Shell. These materials are well established for thermosets, such as epoxy resins, phenolics, and vinyl esters, but modified grades have recently been introduced aiming at thermoplastics, such as styrenic and (significantly, because of its potential in electrical and electronics equipment) ABS. Thermoplastic polyesters, elastomers, and polyolefins can also be flame retarded with these materials which have a bromine content of 50-60% weight... 

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