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首页> 外文期刊>Journal of Applied Polymer Science >Influence of plasticizers suggests role of topology in polymer solidification at high cooling rates
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Influence of plasticizers suggests role of topology in polymer solidification at high cooling rates

机译：增塑剂的影响表明拓扑结构在高冷却速率下在聚合物固化中的作用

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摘要

Although solidification in processing determines short- and long-term properties, methods for understanding polymer crystallization mostly rely on real time experiments. Their evidences being drawn on time scales farther apart with respect to those experienced in processing. Nor significant outcomes have been so far drawn with approaches mimicking the typical processing times, the Continuous Cooling Transformation methods. Use of these techniques has indeed been limited to a heuristic interpretation of the structure developed under extreme solidification conditions without suggesting alternative routes to the understanding or even clues to the many open questions on polymer crystallization under realistic solidification conditions. If the mechanisms inferred from realtime methods cannot in principle be translated to processing conditions the oxymoron is not overcome. In this work, we compare the influence of a plasticizer on the density drop with cooling rate, and therefore on the disappearance of any long range order crystalline phases, observed after fast controlled quenching of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). The plasticizer enhances significantly the maximum cooling rate at which PET still shows long range order crystalline phases, whereas barely modifies the situation for PBT. On the basis of a series of concurrent clues, we suggest that the complex inherent topology of macromolecular melts introduces a timescale on polymer crystallization lying in the range of the solidification conditions experienced in processing. Although melt topology is known to determine in many instances polymer solidification, all approaches so far proposed to describe the development of polymer crystallization overlook or even neglect any explicit dependence of such mechanisms on parameters like the molecular weight between entanglements. Albeit the arguments are feeble they all concur to raise several questions even on the contradictory role of nucleating agents under the extreme conditions experienced in processing.
机译：尽管加工过程中的固化决定了短期和长期性能，但了解聚合物结晶的方法主要依赖于实时实验。他们的证据在时间尺度上比在处理过程中所经历的证据相距更远。到目前为止，还没有采用模仿典型处理时间的方法（连续冷却转化方法）得出明显的结果。实际上，这些技术的使用仅限于对在极端凝固条件下形成的结构进行试探性解释，而没有提出理解的替代途径，甚至不提供关于在实际凝固条件下聚合物结晶的许多未解决问题的线索。如果从实时方法推断的机理原则上不能转化为加工条件，那么就不会克服矛盾现象。在这项工作中，我们比较了聚对苯二甲酸乙二醇酯（PET）和聚对苯二甲酸丁二醇酯（PBT）的快速受控淬火后，增塑剂对密度下降与冷却速率的影响，因此对长程有序晶相消失的影响。增塑剂显着提高了最大冷却速率，在该速率下，PET仍显示出长程有序晶相，而几乎没有改变PBT的情况。根据一系列并发的线索，我们认为高分子熔体的复杂固有拓扑结构为聚合物结晶引入了一个时标，该时标处于加工过程中遇到的凝固条件范围内。尽管已知熔体拓扑在许多情况下决定了聚合物的固化，但迄今为止提出的描述聚合物结晶发展的所有方法都忽略了甚至完全忽略了这种机理对缠结之间分子量等参数的明确依赖。尽管论点微不足道，但它们都同意提出几个问题，即使在成核剂在加工过程中遇到的极端条件下，它们对成核剂的矛盾作用也是如此。

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