Poly heat distortion temperature

Fig. 26. Qualitative compatison of substrate materials for optical disks (187) An = birefringence IS = impact strength BM = bending modulus HDT = heat distortion temperature Met = metallizability WA = water absorption Proc = processibility. The materials are bisphenol A—polycarbonate (BPA-PC), copolymer (20 80) of BPA-PC and trimethylcyclohexane—polycarbonate (TMC-PC), poly(methyl methacrylate) (PMMA), uv-curable cross-linked polymer (uv-DM), cycHc polyolefins (CPO), and, for comparison, glass.

Blends of ABS with polycarbonates have been available for several years (e.g. Bayblend by Bayer and Cycoloy by Borg-Wamer). In many respects these polymers have properties intermediate to the parent plastics materials with heat distortion temperatures up to 130°C. They also show good impact strength, particularly at low temperatures. Self-extinguishing and flame retarding grades have been made available. The materials thus provide possible alternatives to modified poly(phenylene oxides) of the Noryl type described in Chapter 21. (See also sections 16.16 and 20.8.)... 

The use of ABS has in recent years met considerable competition on two fronts, particularly in automotive applications. For lower cost applications, where demands of finish and heat resistance are not too severe, blends of polypropylene and ethylene-propylene rubbers have found application (see Chapters 11 and 31). On the other hand, where enhanced heat resistance and surface hardness are required in conjunction with excellent impact properties, polycarbonate-ABS alloys (see Section 20.8) have found many applications. These materials have also replaced ABS in a number of electrical fittings and housings for business and domestic applications. Where improved heat distortion temperature and good electrical insulation properties (including tracking resistance) are important, then ABS may be replaced by poly(butylene terephthalate). 

This polymer has a slightly stiffer chain and hence slightly higher melting point and heat distortion temperatures than poly(ethylene terephthalate). Films are available (Kodel-Kodak) which have been biaxially stretched about 200% from polymer with molecular weights of about 25 000. They are similar electrically to poly(ethylene terephthalate), are weaker mechanically but have superior resistance to water and in weathering stability. Some properties are given in Table 25.6. 

It has already been shown (e.g. Chapters 20 and 21) that the insertion of a p-phenylene into the main chain of a linear polymer increased the chain stiffness and raised the heat distortion temperature. In many instances it also improved the resistance to thermal degradation. One of the first polymers to exploit this concept commercially was poly(ethylene terephthalate) but it was developed more with the polycarbonates, polysulphone, poly(phenylene sulphides) and aromatic polyketones. 

Mechanical properties are typical of a rigid plastics material and numerical values (Table 30.2) are similar to those for poly(methyl methacrylate). Although thermosetting, it has a low heat distortion temperature ( 80°C) and is not particularly useful at elevated temperatures. 

The heat distortion temperature of impact-resistant polystyrene may also be improved by polymer blends. Those of impact-resistant polystyrene with poly-2,5-dimethylphenylene-1,4-oxide (PPO) are particularly interesting (90). Polystyrene and PPO are molecularly compatible and mixtures of them have glass transition temperatures which vary virtually linearly with composition. A further advantage of these compositions which should not be under-estimated is their better flame resistance. 

Poly(trimethylene terephthalate). Poly(trimethylene terephthal-ate) (PIT) is a crystalline polymer that is used for fibers, films, and engineering plastics. The polymer has an outstanding tensile elastic recovery, good chemical resistance, a relative low melting temperature, and a rapid crystallization rate. It combines some of the advantages of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT). Disadvantageous are the low heat distortion temperature, low melt viscosity, poor optical properties, and pronounced brittleness low temperatures. 

In addition, ASA may be blended with other polymers that themselves exhibit high heat distortion temperatures. For example, blends of poly(ether imide) and ASA exhibit an improved heat distortion temperature, improved flexural properties and tensile properties in comparison to the ASA component alone and have lower impact strengths as well (35). The statement above has been exemplified using Ultem 1000 as a poly(ether imide) resin and Geloy 1020 as ASA component. 

Conversely, ASA itself may serve as a heat distortion improver additive for poly(vinyl chloride) (PVC) (36). The increase of the heat distortion temperature is linearly dependent on the amount of ASA added. Therefore, it is easy to add just the amount needed without doing a lot of preliminary testing with various formulations. ASA can be used in a blend with PVC. Another approach is the coextrusion of the ASA with PVC in such a way that only ASA is exposed to high temperatures. 

A poly ether-amide with a heat distortion temperature of 198°C has been prepared by Hitachi by interfacial polycondensation of 2,2-bis-[4-(4-aminophen-oxy)phenyl]propane (VIII) with a mixture of isophthaloyl- and terephthaloyl-chloride (IX and X) Figure 18.29). 

This synthesis involves a two-step reaction, the first of which yields an intermediate poly(amic acid) that is soluble in polar solvents. In the second, heating to temperatures of about 570 K elfects ring closure to form the insoluble, intractable polyimide. A more direct synthetic method, avoiding the ring closure step, makes use of diisocyanates. KAPTON has an extremely high heat distortion temperature of 630 K and shows exceptional thermo-oxidative resistance. 

Poly(butylene succinate) is often used in blends with other biodegradable polymers like starch [109], PLA [110-114] and PHAs [115,116]. In many cases PBS is added to other biopolymers to improve properties like heat stability (heat distortion temperature) and impact resistance, and to improve processing behaviour. Although PBS and PLA are immiscible, compatibility is sufficient to allow preparation of blends with good mechanical properties [92, 105]. Peroxides can be used to improve the compatibility of the blend leading to improved impact strength [117]. 

High aspect ratio fillers, such as woUastonite and glass fibers can have an even stronger effect than talc and mica on increasing the modulus of elasticity, tensile strength, and heat-distortion temperature of poly(lactic acid) (PLA)-based systems. 

Epichlorohydrin has also been condensed with aromatic and cycloaliphatic polyamines to give resins which can be cured to products with high heat distortion temperatures and low moisture pickup. 1,3,5-Tris(aminomethyl)benzene (20) and cyclohexane (21)/epichlorohydrin condensates have been reported which can be cured to products with heat distortion temperatures in excess of 200°C and with good adhesion. " Poly-... 

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