Crystallization of Polymers and Copolymers at Very High Supercoolings

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

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.