EFFECT OF SOME PHOSPHORUS-COMPOUNDS ON THE THERMOOXIDATIVE STABILITY OF POLY(ETHYLENE-TEREPHTHALATE)

A series of poly(ethylene terephthalate) (PET) samples was prepared fr om dimethyl terephthalate and ethylene glycol. In each sample a phosph orous compound was added as heat stabilizer after the transesterificat ion and before the polycondensation. These compounds were: phosphoric acid, tributyl phosphate, triphenyl phosphate, phenylphosphonic acid, phenylphosphinic acid, and sodium phenylphosphinate. Firstly, their in terference with the transesterification catalyst was examined. Their s tabilization effect was estimated by DSC analysis in nitrogen and air. Various thermal criteria have been used, such as stabilization coeffi cient and induction period of oxidation. Under the conditions used for polymerization, the more efficient stabilizers were tributyl phosphat e, phenylphosphonic and phenylphosphinic acid.