Thermoplastic polyester elastomers

The main disadvantages of these polymers are (in addition to the poor tracking properties)  

It was estimated that in 1987 about 25 companies were involved in the development of liquid crystal polymers, but by 1995 only Hoechst and Amoco were sharing the 3000 t.p.a. global market in the ratio of about 70 30. 

With a typical M of 25 000-30 000 the molecular size is low compared wjth most conventional covalently cross-linked elastomers. With such rubbers M values of about 100000 are desirable so that the effects of a significant amount of non-load-bearing chain ends do not occur. Such a problem does not arise in block copolymers terminated by hard segments. 

In the case of the polycrystalline polyester thermoplastic rubbers the simple domain theory does not seem to apply. With these rubbers it would appear that they contain spherulitic structures consisting of 4GT radial lamellae with inter-radial amorphous regions that are mixtures of PTMEG soft segments and noncrystalline hard segments. 

The polymers available range from those with a stiffness similar to that of polypropylene to that of a rather firm rubber. The harder grades have up to 84% of 4GT segments and a of 214°C whilst the softest grades contain as little as 33% 4GT units and have a T, of 163°C. 

In Chapters 3 and 11 reference was made to thermoplastic elastomers of the triblock type. The most well known consist of a block of butadiene units joined at each end to a block of styrene units. At room temperature the styrene blocks congregate into glassy domains which act effectively to link the butadiene segments into a rubbery network. Above the Tg of the polystyrene these domains disappear and the polymer begins to flow like a thermoplastic. Because of the relatively low Tg of the short polystyrene blocks such rubbers have very limited heat resistance. Whilst in principle it may be possible to use end-blocks with a higher Tg an alternative approach is to use a block copolymer in which one of the blocks is capable of ctystallisation and with a T well above room temperature. Using what may be considered to be an extension of the chemical technology of poly(ethylene terephthalate) this approach has led to the availability of thermoplastic polyester elastomers (Hytrel—Du Pont Amitel—Akzo). 

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Liquid crystal polyesters Polyester Thermoplastic Elastomers Poly(pivalolactone)... 

Polyester thermoplastic elastomers, which are obtained by replacing a part of the R2 diol by dihydroxy polyether macromonomer, present biphasic morphology and rubberlike properties. 

Figure 2.1 Model of microstructure in polyester thermoplastic elastomers.

Ester TPEs. See Polyester thermoplastic elastomers (ester TPEs)... 

Celia R.J., Morphology of segmented polyester thermoplastic elastomers, J. Polym. Set Symp., 42, 727, 1973. 

Witsiepe, W.K., Segmented polyester thermoplastic elastomers, Adv. Chem. Ser., 129, 39, 1973. Srichatrapimuk V.W. and Cooper S.L., Infrared thermal analysis of pol3furethane block polymers, J. Macromol. Set Phys. B, 15, 267, 1978. 

Polymer structure and formulation. As an example, Woo et al. [7] measured OIT values for series of commercial PVC resins and polyester thermoplastic elastomers (TPEs). The researchers used the ASTM D3895-80 procedure, but substituted air as the oxidising gas instead of pure oxygen. A dependency on thermal processing history of the TPE film samples appeared to influence the measured OIT in the PVC study, chemically different chain ends affected polymer stability and hence OIT values. 

High molecular weight PTHF has excellent elastomeric properties but its price is four to five times higher than that of usual rubbers. However, low molecular weight glycols, which are easily prepared from THF and are very useful for the preparation of polyurethanes and polyester thermoplastic elastomers, has been commercially developed inspite of these high costs. 

Solid State NMR Studies of Polyester Thermoplastic Elastomers... 

Uses Flame retardant for thermoplastics (ABS, HIPS, PC), thermosets (unsat. polyester), thermoplastic elastomer wire insulation, adhesives, coatings, textiles, lt.-stable applies. 

Properties Sol. 4 ml in water dens. 3.18 dec. pt. 250 C Uses Flame retardant, smoke suppressant in polymers, esp. PVC and unsat. polyesters, thermoplastic elastomers, wire and cable applies., wall coverings, upholstery ManufJDistrib. Climax Molybdenum Pacific West Trade Names Charmax AOM... 

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