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期刊论文
Determination
CHEM. RES. CHINESE U. 2005, 21(2), 227-231,-0001,():
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 (w) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0.01-100rad/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" (w) us. Lnw curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(w) curve directly. For UHPPH, the G0N 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 G0N has no relation to the molecular weight.
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