Terephthalate polyester, thermal decomposition

A number of studies were done to assess thermal stability of aromatic polyesters. Some of these studies describe flash pyrolysis [27-32]. Some studies are dedicated to slow thermal degradation in an inert atmosphere, and others describe the decomposition in specific conditions such as in the presence of humidity or in the presence of catalysts [33]. For example, thermal decomposition of poly(butylene terephthalate) was significantly influenced by the presence of water vapor, and the amount of the residues decrease with increasing the partial pressure of water in the atmosphere [34]. In another study, thermal stability of some small molecule phthalate esters was studied [35]. The results can be used for inferring information on the thermal stability of related polymers. The influence of substitution on the p-carbon atom was evaluated on compounds such as bis(2-aminobutyl) phthalate, bis(2-nitrobutyl) phthalate, bis(2,4-diphenylbutyl) phthalate, and dineopentyl phthalate. Only the phenyl groups were found to improve the heat resistance by the obstruction of the planar configuration necessary for the c/s-elimination and the hindrance of the formation of a six-membered cyclic transition state. 

A selection of monosubstituted and disub-stituted poly-(/ -phenylene-terephthalate)s is compared in Table 2. Poly(p-phenylene-terephthalate)s with methyl, methoxy, chlo-ro, or bromo substituents on either the hy-droquinone or the terephthalic acid moiety exhibit melting temperatures of 350 °C or higher. Thermotropic liquid crystalline behavior is observed in these samples, although it is in the range of thermal decomposition. A comparison of the mono- and diphenyl substituted polyesters reveals an important trend. The monosubstituted poly-(p-phenylene-terephthalate) with the phenyl substituent in the hydroquinone moiety melts at 346 °C, also forming a nematic melt up to a clearing temperature of... 

Polyethylene terephthalate (PET) is a typical representative of comparatively thermally resistant aryl aliphatic polyesters its thermal decomposition begins at temperatures... 

The following protocol describes a procedure to investigate the effect of humidity on thermal decomposition of terephthalate polyester. The same procedure can be applied to any TG-MS analyses [13]. 

Poly(alkylene terephthalate)s undergo a gradual degradation due to thermal decomposition during processing. This degradation is due to thermal scission, and it is accompanied by a decrease in melt viscosity and a deterioration of the polyester s physical and mechanical properties. 

Polyesters are important thermoplastic resins, which can be obtained by the condensation reaction of glycols and acids or anhydrides 798163. For example, the condensation polymerisation of ethylene glycol or butylene glycol and terephthalic acid produces the well-known polyesters, poly(ethylene terephthalate) (PET) or poly(butylene terephthalate) (PBT), respectively. The mechanism of thermal degradation of polyesters has been studied for many years 817822 776328 756176 670828 with the help of model compounds. However, there is still some current controversy on the crucial point whether the primary thermal decomposition reactions that occur in polyesters involve radical or ionic processes 777330 490068. ... 

As the temperature increases, sequences containing totally aromatic polyester accumulate in the residue, indicating that the overall thermal reaction has resulted in the formation of the most thermally stable compound, i.e., a totally aromatic polyester. As a consequence, the last decomposition stage is solely due to the evolution of the cyclic dimer (ion at m/z 717) formed by tiie thermal degradation of the aromatic polyester sequences (Scheme 5.11c), as confirmed by the DPMS analysis of pure poly(bisphenol A terephthalate). ... 

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