Abstract
AbstractPET-PCT copolyesters were prepared from terephthalic acid (PTA), ethylene glycol (EG) and 1,4-cyclohexane dimethanol (CHDM) through direct esterification and the subsequent polycondensation. The chemical composition and sequence length distribution of the copolyesters were investigated by 1H-NMR and 13C-NMR. The dynamic rheological behavior and dynamic mechanical property were studied by means of ARES-RFS and DMA. The results demonstrated that the obtained PET-PCT copolyesters were random block copolyesters and the content of PCT units incorporated was always greater than the feed and the numberaverage sequence length of each block in the copolyesters was in proportion to its content. The relation between storage modulus (G’) and frequency (freq) deviated from linearity as the frequency (freq) tend to zero (the terminal region effect), and the frequency band where the terminal region effect appeared would shift to higher value with the increasing content of PCT, suggesting the presence of phase separations. Moreover, two glass transition temperatures were observed from DMA curves, which revealed the incompatibility of PET segments and PCT segments, i.e. the micro-phase separation took place in PET-PCT copolyesters.
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