聚氨酯弹性体的取向行为

ORIENTATION BEHAVIORS OF BLOCK POLYURETHANES

聚氨酯弹性体中两种嵌段的取向度有明显差别,软段为0.1～0.2,硬段为0.2～0.4。影响取向度的结构因素主要是软段分子量,硬段的脲键、氢键及其浓度,且主要是对硬段取向度有影响。在90℃时存在取向度的最大值,退火降低取向度。在预应变水平内,预应变增加硬段取向度。取向的结果,导致大量的硬段残留取向、应力软化、应力滞后和高变形,以及材料的高模量和高强度。

The orientation behaviors of block polyurethanes in the process of strain and the differ- ence between two kinds of the block orientation function ,i .e . ,the orientation functions of the soft and hard segments were 0.1 - 0.2 and 0.2 - 0.4 , respectively , were reviewed with 11 references . The major structural factors that affected the orientation functions of polyurethanes were the molecular weights of the soft segments ,and the urea bond ,hydrogen bond and concentration of the hard segments ,and mainly affecting for the hard segments .The temperature of the orientation function passed through a maximum was about 90°C .The orientation functions of hard and soft segments decreased by the annealing of hard segment ,and increased by the prestrain .The orientations of polyurethanes resulted in a large number of the residual orientation , the stress softing and stress hysteresis , the permanent set , the higher modulus and strength of materials .