Hard block length distribution of thermoplastic polyurethane determined by polymerization-induced phase separation
Hard block length distribution of thermoplastic polyurethane determined by polymerization-induced phase separation
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DOI：
10.1016/j.polymer.2022.125236
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发表时间：
2022-08-27
期刊：
影响因子：
4.6
通讯作者：
Wang, Zongbao
中科院分区：
文献类型：
--
作者：
Gao, Zhidong;Wang, Zeyu;Wang, Zongbao
采用手工和机器铸造的方法批量生产了三种基于相同单体和成分的热塑性聚氨酯（tpu）。软段为PTHF (R) 1000，硬段为1,4-丁二醇和4,4 '-亚甲基二苯基二异氰酸酯（MDI）。硬段含量达30%。在80℃和125℃下制备手铸tpu。机器制备样品的温度条件与手工铸造工艺在125℃时的温度条件相当。在高温下制备的样品是透明的，而在低温下制备的样品是半透明的。后者显示出一定的结晶度，在结晶研究中，它比透明样品更容易结晶。透明度和结晶行为的差异归因于硬块长度分布的差异。利用热分馏-一系列连续的自核和退火步骤-可以显示和量化硬块长度分布的微小差异。低温合成的TPU具有较长的硬块。这些物质通过促进成核和晶体生长来促进结晶。上层结构，由较长的硬块引起，散射可见光，降低透明度。
Three thermoplastic polyurethanes (TPUs) based on the same monomers and composition were produced in bulk by hand and machine casting methods. The soft segment was PTHF (R) 1000 and the hard segment was made of 1,4-butanediol and 4,4 '-methylene diphenyl diisocyanate (MDI). The hard segment content amounted to 30%. The hand cast TPUs were prepared at 80 and 125 ?. The temperature conditions for the machine prepared sample were comparable to that of the hand casting process at 125 ?. The samples prepared at high temperature were transparent, whereas the sample produced at low temperature was translucent. The latter showed some crystallinity and in crystallization studies it crystallized more readily than the transparent samples. The distinctions in transparency and crystallization behavior were ascribed to differences in the hard block length distribution. Using thermal fractionation - a series of successive self-nucleation and annealing steps - the minor differences in hard block length distribution could be shown and quantified. The TPU synthesized at low temperatures possessed the longer hard blocks. These facilitated crystallization by enhancing nucleation and crystal growth. Superstructures, induced by the longer hard blocks, scattered visible light and reduced the transparency.