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首页> 外文期刊>Journal of Applied Polymer Science >CRYSTALLINITY AND MORPHOLOGY OF SEGMENTED POLYURETHANES WITH DIFFERENT SOFT-SEGMENT LENGTH
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CRYSTALLINITY AND MORPHOLOGY OF SEGMENTED POLYURETHANES WITH DIFFERENT SOFT-SEGMENT LENGTH

机译：具有不同软段长度的分段聚氨酯的结晶度和形貌

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摘要

A series of polycaprolactone/4,4'-diphenylmethane diisocyanate/1,4-butanediol (PCL/MDI/BDO) segmented polyurethanes of different compositions was synthesized by solution polymerization. The molecular weight of PCL diols used was in the range of 1600-7000. The crystallinity and morphology of these polymers were studied by using DSC, dynamic mechanical analysis, WAXD, and polarizing microscopy methods. It was found that the crystallinity of PCL prepolymers was depressed in segmented polyurethanes. A lower limit of PCL molecular weight was found, below which the PCL segments were not able to crystallize at the usual processing conditions. This limit of molecular weight is in the range of 2000-3000 and exhibits a slight increase with increasing hard-segment content of polyurethanes. The glass transition temperature related to the PCL segment regions in polyurethane specimens deviated from that of pure amorphous PCL prepolymer to a higher temperature. The deviation resulted from the crystallization of PCL segments and also the influence of hard segments. The formation of hard-segment domains becomes very difficult for polyurethanes having low hard-segment content and short hard-segment length. There is a lower limit of hard-segment content and segment length. Only above that limit do the polyurethanes have enough hard-segment domains acting as physical crosslinks at temperatures above the melting point of the PCL crystals. The structural characteristics of segmented polyurethanes which may exhibit a shape memory effect are also discussed. (C) 1996 John Wiley & Sons, Inc. [References: 22]
机译：通过溶液聚合合成了一系列不同组成的聚己内酯/ 4,4'-二苯基甲烷二异氰酸酯/ 1,4-丁二醇（PCL / MDI / BDO）嵌段聚氨酯。所使用的PCL二醇的分子量为1600-7000。通过使用DSC，动态力学分析，WAXD和偏振显微镜方法研究了这些聚合物的结晶度和形态。已发现在链段聚氨酯中PCL预聚物的结晶度降低。发现PCL分子量的下限，低于该上限，在通常的加工条件下PCL链段不能结晶。该分子量的极限在2000-3000的范围内，并且随着聚氨酯的硬段含量的增加而呈现出轻微的增加。与聚氨酯样品中PCL链段区域相关的玻璃化转变温度与纯无定形PCL预聚物的玻璃化转变温度有所不同。偏差是由于PCL段的结晶以及硬段的影响引起的。对于具有低硬段含量和短硬段长度的聚氨酯而言，硬段区域的形成变得非常困难。硬段内容和段长度有一个下限。只有超过该极限，聚氨酯才具有足够的硬段结构域，其在高于PCL晶体熔点的温度下充当物理交联键。还讨论了可能表现出形状记忆效应的嵌段聚氨酯的结构特征。 （C）1996 John Wiley＆Sons，Inc. [参考：22]

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