Glass aromatic polyesters

The nature of the hard domains differs for the various block copolymers. The amorphous polystyrene blocks in the ABA block copolymers are hard because the glass transition temperature (100°C) is considerably above ambient temperature, i.e., the polystyrene blocks are in the glassy state. However, there is some controversy about the nature of the hard domains in the various multiblock copolymers. The polyurethane blocks in the polyester-polyurethane and polyether-polyurethane copolymers have a glass transition temperature above ambient temperature but also derive their hard behavior from hydrogen-bonding and low levels of crystallinity. The aromatic polyester (usually terephthalate) blocks in the polyether-polyester multiblock copolymer appear to derive their hardness entirely from crystallinity. 

PTT has three dynamic mechanical viscoelastic relaxations [61, 62], a, (j and Y (Figure 11.9). The 70°C a-relaxation is the glass transition. In a study on the effect of methylene sequence length on aromatic polyester viscoelastic properties, Farrow et al. [63] reported a PTT a-relaxation as high as 95 °C. They also found that Tg of this series of aromatic polyesters did not show any odd-even effects, which was later confirmed by Smith et al. [64],... 

Havens and Bell performed an electron beam irradiation of methylene-bridged aromatic polyesters, which were synthesized by polycondensation between two pairs of aromatic diacid chlorides and 3,3 -methylenediphenol or 4,4 -methylenediphenol [54]. They found that irradiation of thin films of these polyesters at room temperature resulted in some chain extension and cross-linking, and that irradiation at a temperature near or above the glass transition temperatures of the polymers greatly enhanced the tendency for the polymers to crosslink. 

Here the differences in the melting temperatures and in the glass temperatures are even greater than in Tables II and III. Large differences are encountered on comparing a purely aliphatic polyester with a highly aromatic polyester (cf. Table V). A polyester of adipic acid and... 

Table 4. The Glass Transition and Melting Temperatures of Branched Aromatic Polyesters...

The glass transition temperature does not change significantly with composition. However, the melting point increases with the amount of 4-acetoxybenzoic acid, which is less bulky than 3-benzoyl -acetoxybenz-oic acid. Aromatic polyesters are highly heat resistant due to their high crystallinity. 

Polyesters. Main chain of their macromolecules is characterized by repeated — CO—O— groups. Unsaturated polyester resins are thermosets used mainly for manufacturing glass fibre-reinforced plastics products. The most wide-spread type of thermoplastic polyesters are polymers of an aromatic dicarboxylic acid (mainly terephthalic acid) and an aliphatic diol (e. g. ethyleneglycol or butanediol). The most important representatives of this group are poly(ethylene terephthalate) and poly-(butylene terephthalate). Polyarylate aromatic polyester is a high-temperature thermoplastic of an aromatic dicarboxylic acid (terephthalic acid) and an aromatic diol (bisphenol-A). In the chemical sense, polycarbonate is also a polyester. 

Wholly aromatic polyesters from dihydric phenols and dicarboxyUc acid chlorides. They are characterized by high melting point (up to 500 °C), good thermal stability, and solubility in chlorinated solvents. Commercial polymers are produced by polycondensation of iso- and terephthalic acids with bisphenol A, having glass transition temperatures near 170 °C and the continuous use temperature of 140-150 °C. 

Copolyesters have also been synthesized by interfacial polycondensation, with aromatic-aliphatic structures. The introduction of an aliphatic diol into aromatic polyester was found to influence glass-transition temperature, softening point, and chemical and thermal stability. Trans-gauche rotational isomers in poly(ethylene terephthalate) in fibre form have also been produced," as have lactide-glycolide copolyesters. "... 

Studies on the amorphous state of 2GT have beoi restricted to Brillouin scattering and DSC studies on changes of the amorphous state afforded by heat treatment below the glass transition temperature. Broad line n.m.r. studies and dynamic mechanical behaviour of some aromatic polyesters have been reported and the data related to the transition behaviour in these systems." The thermal behaviour, mechanical properties, and supramolecular texture in polyOiexa-methylene terephthalate)-poly(oxytetramethylene) block copolymer systems has been compared to that of the homopolymers and related to composition and phase separation morphology."- ... 

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