Thermoplastic vulcanizates (TPVs) are a special class of polymer blends comprised of a thermoplastic polypropylene (PP) matrix and a dynamically vulcanized ethylene propylene diene monomer (EPDM) rubber. Due to the presence of crosslinked rubber particles, TPVs exhibit complex rheological fingerprints similar to those of soft elastic solids. In this study, we attempt to draw a correlation between the rheology of several TPVs to the base components, namely, PP and EPDM. The effects of long chain branching of the primary constituents (prior to crosslinking), the level of curing, and the amount of crosslinked rubber on their rheology are studied in detail and found to affect the rheology to various degrees. All TPVs studied exhibited a universal relaxation modulus of the form ( G ( t ) − G y ′ ) ∝ t − p, where G y ′ is the equilibrium modulus indicating the elastomeric nature of TPVs (increases with the rubber crosslink density) and the absence of terminal relaxation with a proportionality constant dependent on the constituent polymer combination, the level of curing, and rubber concentration. At high deformations, these complex materials yield in both shear and extensional flows, and relevant stresses are determined and compared. While yield stress in shear can be easily determined, for the first time the yield stress in extension is observed and reported for polymer melts.

中文翻译：

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热塑性硫化橡胶 (TPV) 的流变学

热塑性硫化橡胶 (TPV) 是一类特殊的聚合物共混物，由热塑性聚丙烯 (PP) 基体和动态硫化的三元乙丙橡胶 (EPDM) 橡胶组成。由于交联橡胶颗粒的存在，TPV 表现出类似于软弹性固体的复杂流变指纹。在本研究中，我们试图将几种 TPV 的流变学与基础组分（即 PP 和 EPDM）的相关性联系起来。详细研究了主要成分的长链支化（交联前）、硫化水平和交联橡胶的量对其流变学的影响，发现对流变学有不同程度的影响。所有研究的 TPV 都表现出形式为 ( G ( t ) − G y ′ ) ∝ t − p 的通用松弛模量，其中 G y ' 是平衡模量，表明 TPV 的弹性性质（随橡胶交联密度增加）和不存在末端松弛，其比例常数取决于组成聚合物组合、固化水平和橡胶浓度。在高变形下，这些复杂的材料在剪切流和拉伸流中都会屈服，并确定和比较相关应力。虽然剪切屈服应力很容易确定，但第一次观察和报告了聚合物熔体的拉伸屈服应力。这些复杂的材料在剪切流和拉伸流中都会屈服，并确定和比较相关应力。虽然剪切屈服应力很容易确定，但第一次观察和报告了聚合物熔体的拉伸屈服应力。这些复杂的材料在剪切流和拉伸流中都会屈服，并确定和比较相关应力。虽然剪切屈服应力很容易确定，但第一次观察和报告了聚合物熔体的拉伸屈服应力。