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首页> 外文期刊>Macromolecules >Real-time micro-Raman measurements on stressed polyethylene fibers. 1. Strain rate effects and molecular stress redistribution
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Real-time micro-Raman measurements on stressed polyethylene fibers. 1. Strain rate effects and molecular stress redistribution

机译：在受压聚乙烯纤维上进行实时微拉曼测量。 1.应变率效应和分子应力的重新分布

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The molecular deformation of ultrahigh-molecular-weight polyethylene monofilaments was monitored in real time by remote laser Raman microscopy(ReRaM). A shift to lower wavenumbers of the symmetric and asymmetric C-C stretching mode bands, was observed in agreement with previously published data. The stress or strain dependence of the Raman wavenumbers as a function of strain rate was also examined at room temperature. Furthermore, the broadening of the Raman bands as a function of applied stress or strain was investigated and compared with the wavenumber shift in each case. The Raman band shift for the asymmetric and symmetric C-C stretching modes per stress or strain was found to be only marginally affected for strain rates ranging from 10(-4) to 10(-3) s(-1). The onset of the observed dramatic decrease of the Raman wavenumbers as a function of stress or strain was directly related to the existence of two yield points. The first "yield" point at relatively low applied strain/stress is thought to be associated with the plastic flow of the amorphous part. The second "yield" point at high strain/stress is possibly associated with the initiation of microcracking, which leads to the ultimate failure of the fiber. Finally, the corresponding band broadening indicated the presence of a highly nonuniform stress field acting upon the molecules of the crystalline fraction that give rise to the broad symmetric C-C and asymmetric stretching modes. A number of structural models have been reviewed in the light of the Raman data presented here. [References: 27]
机译：通过远程激光拉曼显微镜（ReRaM）实时监测超高分子量聚乙烯单丝的分子变形。与先前发表的数据一致，观察到对称和不对称C-C拉伸模式带的波数较低。还在室温下检查了拉曼波数的应力或应变依赖性与应变率的关系。此外，研究了拉曼谱带的扩展随所施加的应力或应变的变化，并与每种情况下的波数偏移进行了比较。发现每个应力或应变的不对称和对称C-C拉伸模式的拉曼带位移仅对应变率从10（-4）到10（-3）s（-1）的影响很小。拉曼波数作为应力或应变的函数的急剧下降的发生与两个屈服点的存在直接相关。在相对较低的施加应变/应力下的第一个“屈服”点被认为与非晶态零件的塑性流动有关。高应变/应力下的第二个“屈服”点可能与微裂纹的产生有关，这导致了纤维的最终破坏。最后，相应的谱带展宽表明存在高度不均匀的应力场，该应力场作用于结晶级分的分子上，从而导致宽的对称C-C和非对称拉伸模式。根据此处介绍的拉曼数据，已经审查了许多结构模型。 [参考：27]

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