Polyolefinic thermoplastic vulcanizates (TPVs) composed of iPP (isotactic polypropylene) and crosslinked EPDM (ethylene-propylene-diene rubber) prepared by dynamic vulcanization process exhibit rubber domains dispersed in the iPP matrix, even though the EPDM component is the major component. Here we proposed a kinetic nonequilibrium constitutive equation that considers the transition of the mechanical nature from plasto-rigid deformation to rubbery deformation during uniaxial extension to explore the origin of the thermoplastic elastomer behavior of TPV (thermoplastic vulcanizate) materials. Fitting of the constitutive equation to the experimental stress‒strain curves quantitatively revealed the critical transition point of the mechanical properties. The transition shifted to higher strains with decreasing EPDM content. In situ wide-angle X-ray diffraction profiles monitored during the uniaxial extension confirmed the mechanical transition process.

中文翻译：

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聚烯烃热塑性硫化橡胶拉伸行为的非平衡本构方程


由 iPP（等规聚丙烯）和通过动态硫化工艺制备的交联 EPDM（三元乙丙橡胶）组成的聚烯烃热塑性硫化橡胶（TPV）显示出分散在 iPP 基体中的橡胶域，尽管 EPDM 组分是主要组分。在这里，我们提出了一个动力学非平衡本构方程，考虑单轴拉伸过程中机械性质从塑性刚性变形到橡胶变形的转变，以探索 TPV（热塑性硫化橡胶）材料的热塑性弹性体行为的起源。本构方程与实验应力-应变曲线的拟合定量揭示了力学性能的临界转变点。随着 EPDM 含量的减少，这种转变转向更高的应变。在单轴延伸过程中监测的原位广角 X 射线衍射图证实了机械转变过程。