Dibasic-acid-modified PCT Copolyester Preparation and Properties

DIBASIC-ACID-MODIFIED PCT COPOLYESTER PREPARATION AND PROPERTIES 

The crystallinity of PCT can be modified witli diacids as well as with diols and these modified polyesters are often called acid-modified PCTs, or abbreviated as PCTAs. The most common diacid modifier is isophdialic acid (IPA), which can be incorporated in relatively low levels to lower die melting point of PCT to enhance processability while still maintaining ciystallinity. The high Tin of PCT (295 °C) requires that the homopolymer be processed at temperatures greater than 300 °C, which is near the decomposition temperature [13]. 

Low-level incorporation of IPA (5-10 mol %) widens the processing window by lowering the melting point of the polyester while also retaining the crystallinity, Tg and toughness of the PCX homopolymer. At higher IPA incorporation levels, chain crystallization is severely restricted so tliat at 35 mol % of IPA and higher, the amorphous copolyesters do not crystallize without the addition of an added nucleator [55-59]. 

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