聚丙烯熔体流动指数与分子量及其分布的关系

Dependence of melt index on molecular weight and molecular weight distribution of polypropylene

研究了聚丙烯(PP)的熔体流动指数(MI)与聚合物不同分子量之间的关联性,对于分子量分布较窄的PP,数均分子量(Mn)、重均分子量(Mw)和粘均分子量(Mv)均能较好的关联;反之,MI与Mn关联性下降,而MI与Mw和Mv的关联性仍很好,尤其是MI与Mv的关联性受分子量分布的影响很小;MI与Z均分子量的关联性很差。同时,确定了MI与各种分子量之间的关联式.该式用于本体PP工艺反应器内氢气浓度的计算和MI的预测,与实验测量结果吻合良好。

The dependence of melt index (MI) of polypropylene (PP) on different molecular weights of polymers was studied. As far as the PP having narrow molecular weight distribution was concerned. There existed a close dependence of MI on number-average molecular distribution (Mn), weight-average molecular weight (Mw) and viscosity-average molecular weight distribution (Mv), respectively. On the other hand, in case of a polymer with a broad molecular weight, the dependence of MI on Mn was weakened and the correlation between MI and Mw or M, was still well tenable. Especially the dependence of MI on Mv was hardly influenced by molecular weight distribution. The dependence of MI on atomic number molecular weight distribution was not clearly defined. At the same time, a series of equations for the correlation between MI and different molecular weights were established, which could be used for calculating the hydrogen concentration inside the PP reactor and predicting the MI of the PP resins. The data so acquired was well conformed to the values measured in the experiments.