论文部分内容阅读
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 ethylene-propylene 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(G 0_N) of UHPPH from a certain experimental temperature G″(ω) curve directly. For UHPPH, the G 0_N determined to be 4.28×10 5 and 3.62×10 5 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 G 0_N has no relation to the molecular weight.
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 ° C, whose loss modulus (G “) plots at 180 and 200 ° C versus the natural logarithm of angular frequency (ω) at 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 ethylene-propylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact that that high molecular weight is responsible for a maximum peak of G ”(ω) vs. lnω curves for UHPPH. This makes it For UHPPH, the G 0_N determined to be 4.28 × 10 5 and 3.62 × 10 5 Pa at 180 and 200 ° C., and the plateau modulus (G 0_N) of UHPPH from a certain experimental temperature G "(ω) respectively, decreases with the increas e of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G 0_N has no relation to the molecular weight.