Flow induced crystallization of long chain branched polypropylenes under weak shear flow
Flow induced crystallization of long chain branched polypropylenes under weak shear flow
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DOI：
10.1016/j.eurpolymj.2009.03.011
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发表时间：
2009-07
影响因子：
6
通讯作者：
Fengyuan Yu;Hongbin Zhang;R. Liao;Hong Zheng;Wei Yu;Chi-xing Zhou
中科院分区：
文献类型：
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作者：
Fengyuan Yu;Hongbin Zhang;R. Liao;Hong Zheng;Wei Yu;Chi-xing Zhou
本文采用线型聚丙烯与多官能团单体通过熔融接枝反应制备了长链支化聚丙烯(LCB PP)聚合物。采用定量流变学方法对LCB PP的结构参数进行了分析。用流变学、差示扫描量热法、偏光显微镜和广角X射线衍射仪研究了支化程度对PP结晶动力学的影响。LCB PP的动态粘弹性能表明，在长松弛时间区，支化程度的增加导致熔体弛豫谱的分布与末端行为发生明显偏离。发现支链水平对PP熔体的流动诱导结晶(FIC)过程有显著影响。在低剪切速率下，在诱导期内，LCB PP的结晶对剪切流动比线性PP更敏感。这一结果还表明，较长的高分子链的松弛时间对剪切流场作用下的PP成核起重要作用。与低链支化程度的LCB PP相比，高链支化程度的LCB PP表现出更快的结晶动力学。
In the present work long chain branched polypropylene (LCB PP) polymers were prepared by linear polypropylene and multi-functional monomer through melt grafting reaction. A quantitative rheological method was adopted to analysis the structure parameters of LCB PP. The effects of chain branched level on the crystallization kinetics of PP were investigated by rheology, differential scanning calorimetry, polarized optical microscope and wide-angle X-ray diffraction. The dynamic viscoelastic properties of LCB PP showed that the increase in the chain branched level caused a typical deviation from the terminal behavior and a different distribution of the melt relaxation spectrum in the long relaxation time regime. It was found that the chain branched level had a significant effect on the flow induced crystallization (FIC) process of PP melts. The crystallization of LCB PP was more sensitive to shear flow than that of linear PP during induced period at low shear rates. This result also indicated that the longer relaxation time of the polymer chains played an important role in the nucleation of PP under shear flow fields. LCB PP with high chain branched level showed accelerated crystallization kinetics in comparison with that with low chain branched level.