CHDM-modified PET Copolyester Preparation and Properties

CHDM is a very effective crystallization modifier for PET and as stated earlier low-level modification yields crystalline polyesters (PETGs) that are important 

The crystallinity of PCT can be modified with 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 isophthalic acid (IPA), which can be incorporated in relatively low levels to lower the melting point of PCT to enhance processability while still maintaining crystallinity. The high Tm 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 PCT homopolymer. At higher IPA incorporation levels, chain crystallization is severely restricted so that at 35 mol % of IPA and higher, the amorphous copolyesters do not crystallize without the addition of an added nucleator [55-59], 

---