Induced crystallinity during stretch-blow moulding process and its influence an mechanical strength of poly(ethylene terephthalate) bottles

Microstructural evolution in poly(ethylene terephthalate) during a stretch- blow process has an important influence on the final mechanical properties. To obtain information other than thickness distributions from numerical si mulations of the blow moulding process, it is necessary to take into accoun t the evolution of these characteristics (molecular orientation, crystallin ity, etc). Numerical simulations of top loading tests at ambient temperatur e have been carried out on bottles and compared with experimental results. Good agreement was obtained if appropriate anisotropic moduli were used. In the present paper, results of tensile measurements made on stretch-blow mo ulded samples and experimental tensile tests on poly(ethylene terephthalate ) specimens are presented. The influence of draw ratio, temperature, and el ongational strain rate on the final strength of the bottle are analysed. A correlation between the mechanical characteristics and the induced crystall inity is demonstrated and used to predict mechanical characteristics at dif ferent locations on the bottle. PRC/1542 (C) 1999 IoM Communications Ltd.