Elasticity and inelasticity of thermoplastic polyurethane elastomers: Sensitivity to chemical and physical structure
Elasticity and inelasticity of thermoplastic polyurethane elastomers: Sensitivity to chemical and physical structure
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DOI：
10.1016/j.polymer.2010.04.069
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发表时间：
2010-06-24
期刊：
影响因子：
4.6
通讯作者：
Martin, C.
中科院分区：
文献类型：
--
作者：
Buckley, C. P.;Prisacariu, C.;Martin, C.
研究了14种聚氨酯弹性体的循环拉伸响应，讨论了它们的化学组成和物理结构。改变硬链段、软链段和扩链剂，同时将硬链段分数保持在约40%，软链段摩尔质量保持在2000 g/mol。硬链段由4，4 '-亚甲基双（苯基二异氰酸酯）（MDI）或4，4'-二苄基二异氰酸酯（DBDI）产生。物理结构的特征在于通过X射线散射（SAXS和WAXS），揭示显着的相分离程度和结晶度的变化，特别是在DBDI为基础的聚合物。在第一次加载到一个给定的应变的机械响应中发现了很大的差异。拉伸模量和功输入随硬相结晶度的增加而显著增加，但与相分离程度无关。发现第一循环滞后随着相分离减少和用DBDI代替MDI而增加。然而，在第二次和随后的载荷循环中，观察到了Mullins效应，发现了反应的显著均匀性。一个独特的线性关系，获得第二个循环滞后和第二个循环工作输入之间，对于所有的应变水平，和所有的材料，除了两个（具有最高的相分离），表现出略低的第二个循环滞后。的结果可以解释在第一个周期的硬相的片段拉出，形成一个新的串联耦合的软相，其本构响应，然后出现几乎独立的化学和物理结构。(C)2010爱思唯尔有限公司版权所有。
Cyclic tensile responses of fourteen polyurethane elastomers were studied, with respect to their chemical composition and physical structure. Hard segment, soft segment and chain extender were varied, while keeping the hard segment fraction at ca 40% and soft segment molar mass at 2000 g/mol. Hard segments were generated from 4,4'-methylene bis(phenyl di-isocyanate) (MDI), or 4,4'-dibenzyl di-isocyanate (DBDI). Physical structure was characterized by X-ray scattering (SAXS and WAXS), revealing significant variations in degree of phase separation and degree of crystallinity, especially in the DBDI-based polymers. Large differences were found in the mechanical responses during first loading to a given strain. Tensile modulus and work input increased significantly with degree of hard phase crystallinity, but were independent of degree of phase separation. First cycle hysteresis was found to increase with reduced phase separation and with replacement of MDI by DBDI. In second and subsequent load cycles, however, in which the Mullins effect was observed, a remarkable degree of uniformity of response was discovered. A unique linear relation was obtained between second cycle hysteresis and second cycle work input, for all strain levels, and for all materials except for two (with highest phase separation) which showed slightly lower second cycle hysteresis. The results can be explained in terms of pull-out of segments from the hard phase on the first cycle, to form a new series-coupled soft phase, whose constitutive response then appears almost independent of chemical and physical structure. (C) 2010 Elsevier Ltd. All rights reserved.