Effet de l'architecture de chaîne sur le comportement en injection soufflage de copolyesters PET. - Etude expérimentale

摘要

Polyethylene terephthalate, or PET, is mainly used to produce bottles, generally by injection blowing. Inthis study, we point out, for each step of this process, differences of behaviour between severalcopolyesters having a controlled composition. Our attention focus principally on nature of introducedcomonomers, beyond ethylene glycol and terephthalic acid, and length of chains. Thus major solicitationssuffered by material during the bottle forming are reproduced by laboratory tests. We show that kinetic ofstatic crystallization, measured by DSC, could define cooling conditions to assure the amorphous natureof injected preforms. Moreover, blowing range, i.e. rubberized state, is obtained by DMA. Our resultsindicate too that it is necessary, to grasp behaviour during blowing, to consider a minimum of sixcharacteristics of polymer which could be temperature, elastic modulus, rate dependence of materialresponse, hardening strain and stress, and finally bi-axiality disequilibrium of hollow body forming. Lastlyit appears that material adapts its stress way to the solicitation according its rheology, which determinesbottle properties, notably in term of orientation or crystallisation.