Crystallization of Polymers and Copolymers at Very High Supercoolings

聚合物和共聚物在与工业加工操作有关的条件下的固化对于聚合物的设计和所有形式的塑料工业的运行都是相当重要的。最受欢迎的条件之一是结晶聚合物不能在高过冷度或低温下研究，因为聚合物通常在达到所需的等温条件之前固化。其中两种聚合物是线性聚乙烯和尼龙66。最近开发的Ding-Sprueill快速冷却方法，利用嵌入样品中的微型热电偶，直接连续测量温度，已被证明以意想不到的方式克服了这一困难。由于聚合物薄膜被迅速冷却，结晶热使聚合物保持在由冷却和放热的相对速度决定的恒定温度。这项拟议的研究旨在继续目前对聚乙烯及其共聚物的成功研究，这些研究导致了聚合物结晶的新规律的发现。这些定律以前没有在实验中观察到，也没有任何可用的理论预测。此外，还建议将该方法应用于尼龙66及其共聚物。在目前的NSF支持下，P.I的小组已经表明，与其他聚合物体系不同，尼龙66及其共聚物不遵循二次成核作为晶体生长的机制。因此，它们组成了一组独特的聚合物，这些聚合物遵循表面粗化作为生长机制。这项拟议的研究旨在阐明这两种基础物理感兴趣的通用形式的结晶机理，帮助解决目前关于结晶机理的几个争议，同时加深对两种非常重要的工业聚合物在直接适用于制造操作的条件下的结晶行为的理解。实验将包括在迄今无法达到的条件下在宽的结晶温度范围内形成的详细形貌的研究，以及结晶动力学和熔化行为的研究。实验方法包括透射电子显微镜、原子力显微镜、光学显微镜、小角x射线散射和小角中子散射。

The solidification of polymers and copolymers under conditions relevant to industrial processing operations is of considerable importance to the design of polymers and to operation of the plastics industry in all its forms. One of the most sought after conditions is crystalline polymers cannot be studied at high supercoolings, or low temperatures as the polymers usually solidify before the desired isothermal condition can be achieved. Two of those polymers are linear polyethylene and nylon 66. The recently developed Ding-Sprueill method of rapid cooling which utilizes a micro-thermocouple embedded in the sample and direct continuous measurement of temperature has proved to over come the difficulties in an unexpected way. As the polymer film is cooled rapidly the heat of crystallization maintains the polymer at a constant temperature determined by the relative rates of cooling and heat liberation. The proposed research seeks to continue current successful studies of polyethylene and its copolymers, which have led to the discovery of new laws of polymer crystallization. These laws have not been observed previously experimentally, nor are they predicted by any available theories. It is proposed additionally to apply the method to nylon 66 and its copolymers. The P.I's group, under current NSF support, have shown that nylon 66 and its copolymers do not follow secondary nucleation as the mechanism of crystal growth, unlike other polymer systems. They therefore compose a unique group of polymers that follow surface roughening as the mechanism of growth. The proposed research is intended to shed considerable light on the mechanism of crystallization of these two generic forms of interest to basic physics, assist in resolving several current controversies on mechanisms of crystallization, and at the same to generate understanding of the crystallization behavior of two very important industrial polymers under conditions which are directly applicable to manufacturing operations. Experimentation will include studies of detailed morphologies developed over wide crystallization temperature ranges under conditions hitherto unattainable as well as studies of the crystallization kinetics and the melting behavior. Experimental methods to be used include transmission electron microscopy, atomic force microscopy, optical microscopy, small angle x-ray scattering and small angle neutron scattering.%%%This research is in the area of structure, crystallization and processing of industrially important polymeric materials.