Abstract: PET is one of the most important commercial polymer and much effort is being made to modify PET by melt copolymerization with a second glycol or diacid comonomer in a way that yields an amorphous material with a high Tg. In this study, various amounts (0–100 %) of tricyclodecanedimethanol (TCDDM) were used to copolymerize ethylene glycol and terephthalic acid to form a series of c…