A NEW ELECTRIC INSULATING FILM - POLY(ETH YLENE-TEREPHTHALATE P-OXYBENZOATE)

A series of copolyesters poly(ethylene terephthalate p-oxybenzoate) (P ETO). derived from terephthalic acid, ethylene glycol and 4,4'-oxybis( benzoic acid) were easily prepared by using DMT method and thermally i nvestigated. Introduction of 4,4'-oxydiphenylene group into the main c hain resulted in a lowering of T-m, a decrease of crystallization rate and an increase of thermal-oxidative stability of the copolyesters. B y static elongation of PETO, transparent films with qualified electric al properties and mechanical properties were easily obtained with film forming rate 100%. In comparison with poly (ethylene terephthalate)(P ET) film, PETO film had obviously low T-m and low crystallization temp erature. Due to the presence of stable aromatic ether structure, decre ase in T-m could not lead to any reduction in thermal-oxidative stabil ity, on the contrary, slight increase was observed. PETO film could be used in making heat resistant thick film for channel insulators of el ectric motor.