Relations entre Indice de Fluidite à Chaud, Viscosité à l'État Fondu, Viscosité Intrinsèque et Température pour le Poly(éthylène Térèphtalate) et pour un Poly(éthylène Térèphtalate) Partiellement Modifié

Abstract

Methods for the determination of melt index and melt viscosity of poly(ethylene terephtalate) (PET) were performed. Measurements of melt index at different temperatures and of melt and intrinsic viscosity were carried out on laboratory samples. Relations have been obtained and theoretically interpreted among the above parameters. These relations allowed us to utilize melt index data in order to estimate melt viscosities and molecular sizes of PET. Melt indexes were found to be inversely proportional to newtonian melt viscosities. The relations among intrinsic viscosity, melt viscosity, and melt index, respectively, were found to be linear in a log-log plot. The effect of temperature on melt index values was found to agree with the Andrade equation. The energy of activation of the viscous flow was calculated and showed a slight dependance on molecular weight. Measurements were also carried out on an adipic acid–terephtalic acid–ethylene glycol copolymer. It was possible also in this case to obtain relations among the above parameters which were similar to the ones obtained for PET. However, the melt viscosity of the copolymer was always lower than the one of PET at the same intrinsic viscosity. This effect was attributed to an increase in chain flexibility.