Abstract This work presents novel findings on the rheological properties of self-nucleated polymer melts. Different polycaprolactones (PCL) with varying molar masses were investigated with shear rheometry, assessing the viscoelastic functions at different temperatures, reached either from the melt or from the semi-crystalline state. The latter condition produces a self-nucleated melt, in which residual clusters of unclear nature enhance the re-crystallization process, while a homogeneous melt is obtained with the first protocol. Striking differences are observed in melts with or without self-nuclei. The Newtonian viscosity and flow activation energy increase up to one order of magnitude with respect to the fully equilibrated melt. The plateau modulus also shows a remarkable increment, indicating an apparent decrease of the molecular weight between entanglements. The results demonstrate the existence of an additional attractive intermolecular interaction between chain segments in self-nucleated PCL melts, able to provide “extra” physical entanglements which progressively dissolve as the temperature is raised. Self-nucleated propene/ethylene copolymers analyzed in previous work display much weaker effects. The apparent discrepancy is discussed in light of the differences in intermolecular interactions and melting enthalpies between the two polymers.

中文翻译：

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自成核聚（ɛ-己内酯）熔化的流变学

摘要 这项工作提出了关于自成核聚合物熔体流变特性的新发现。使用剪切流变测定法研究了具有不同摩尔质量的不同聚己内酯 (PCL)，评估了不同温度下的粘弹性函数，从熔体或半结晶状态达到。后一种条件产生自成核熔体，其中性质不明的残留簇增强了重结晶过程，而第一个协议则获得了均匀的熔体。在有或没有自核的熔体中观察到惊人的差异。相对于完全平衡的熔体，牛顿粘度和流动活化能增加了一个数量级。平台模量也显示出显着的增量，表明缠结之间的分子量明显降低。结果表明，自成核 PCL 熔体中链段之间存在额外的有吸引力的分子间相互作用，能够提供“额外”的物理缠结，随着温度的升高逐渐溶解。在之前的工作中分析的自成核丙烯/乙烯共聚物显示出更弱的效果。根据两种聚合物之间分子间相互作用和熔融焓的差异讨论了明显的差异。在先前的工作中分析的自成核丙烯/乙烯共聚物显示出更弱的效果。根据两种聚合物之间分子间相互作用和熔融焓的差异讨论了明显的差异。在先前的工作中分析的自成核丙烯/乙烯共聚物显示出更弱的效果。根据两种聚合物之间分子间相互作用和熔融焓的差异讨论了明显的差异。