分子量分布对聚酯性能的影响

研究了不同分子量分布聚酯的热性能、结晶性能和熔体挤出性能。结果表明,随分子量分布加宽,熔体结晶峰的峰温逐步升高,过冷程度降低,蜂形由宽矮形变为高尖形,而冷结晶峰峰温逐渐降低,峰形由宽变窄。同时,随分布加宽,结晶速度加快。在等混结晶过程中,在180℃附近出现结晶速度极大值,而且此极大值与分子量分布无关。此外,随分子量分布加宽,聚酯热稳定性略为下降,在熔体挤出过程中的粘度降增大,挤出过程迅速恶化,以致于难以成形。

EFFECT OF THE MOLECULAR WEIGHT DISTRIBUTION ON PET PROPERTY

The thermal property, crystallization behavior and melt extrudability of PETwith different MWD(Molecular Weight Distribution) were studied. The results sh-ow that as MWD of PET widens, the peak temperature of melt crystallization ris-es, overcooling extent of samples decreases and the shape of the peaks changes fromshort-wide shape into tall-narrow one, meanwhile, the crystallization rate increa-ses. During isothermal crystallization, there appears a maximum value in crystall-ization rate at about 180℃, which is independent of the width of MWD. Moreover,the thermal stability of PET decreases slightly. During the extrudation of melt,the viscosity drop of PET increases, the extrudability of melt becomes so difficultthat the fiber can hardly be formed,