Amorphous Copolyesters of PET

In theory, almost any comonomer diacid or dialcohol could lead to amorphous copolymers of PET. For example, incorporation of 20-80% of 2,6-naphthalate, or greater than 30% of isophthalate, will generate amorphous materials [9]. Amorphous copolymers of PET, produced by the wholesale substitution of other monomers into the polymeric backbone, rarely possess desirable thermomechanical properties, unlike the Eastman PETG compositions. 

Alternative monomers for elimination of crystallinity in PET have been recently proposed. In each of these cases, cyclic monomers were employed, and in most cases, these monomers were alicyclic, and potentially possess sub-Tg molecular motions that could also be of help in dissipating impact energy tlirough molecular motions. The four-membered ring monomer, 2,2,4,4-tetrametiiyl-l,3-cyclobutanediol (CBDO), first developed by the Shell Chemical Company, has 

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