Thermal behavior and tensile properties of poly(ethylene terephthalate-co-ethylene isophthalate)

Poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) ho mopolymers were synthesized by the two-step melt polycondensation process o f ethylene glycol (EG) with dimethyl terephthalate (DMT) and/or dimethyl is ophthalate (DMI), respectively. Nine copolymers of the above three monomers were also synthesized by varying the mole percent of DMI with respect to D MT in the initial monomer feed. The thermal behavior was investigated over the entire range of copolymer composition by differential scanning calorime try (DSC). The glass transition (T-g), cold crystallization (T-cc), melting (T-m), and crystallization (T-c) temperatures have been determined. Also, the gradually increasing proportion of ethyleno-isophthalate units in the v irgin PET drastically differentiated the tensile mechanical properties, whi ch were determined, and the results are discussed. (C) 2000 John Wiley & So ns, Inc.