A series of copolyesters poly(ethylene terephthalate p-oxybenzoate) (PETO) de-rived from terephthalic acid, ethylene glycol and 4, 4’ -oxybis (benzoic acid) were easily pre-pared by using DMT method and thermally investigated. Introduction of 4, 4’ -oxydipheny-lene group into the main chain resulted in a lowering of Tm. a decrease of crystallization rate and an increase of thermal-oxidative stability of the copolyesters. By static elongation of PETO, transparent films with qualified electrical properties and mechanical properties were easily obtained with film forming rate 100%. In comparison with poly (ethylene terephthalate) (PET) film, PETO film had obviously low Tm. and low crystallization temper-ature. Due to the presence of stable aromatic ether structure, decrease in Tm. could not lead to any reduction in thermal-oxidative stability, on the contrary, slight increase was ob-served. PETO film could be used in making heat resistant thick film for channel insulators of electric motor.
