高等学校化学研究 ›› 2005, Vol. 21 ›› Issue (2): 227-231.
DING Jian, DING Xue-jia, XU Ri-wei, YU Ding-sheng
DING Jian, DING Xue-jia, XU Ri-wei, YU Ding-sheng
摘要: The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G") plots at 180 and 200 ℃ versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100 rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD.The fact indicates that the high molecular weight is responsible for a maximum peak of G"(ω) vs.lnω curves for UHPPH.This makes it possible to determine the plateau modulus (GN0) of UHPPH from a certain experimental temperature G"(ω) curve directly.For UHPPH, the GN0 determined to be 4.28×105 and 3.62×105 Pa at 180 and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the GN0 has no relation to the molecular weight.