Growth, morphology, and reinforcement potential of low molecular weight crystals in amorphous polymeric matrices

Abstract

The technique of in situ crystallization of low molecular weight organic compounds from amorphous polymers was evaluated as a method of fabricating composite materials. Two workable systems, styrene–acrylonitrile copolymer (SAN)–acetanilide and SAN–anthracene, were found and their phase diagrams determined. In both systems kinetic studies revealed that the maximum crystallization rate takes place at large degrees of supercooling and that below these temperatures the mechanism is diffusion‐controlled. The temperature‐dependent crystal morphologies were characterized with electron microscopy, which showed three distinctly different morphologies for both systems. From dynamic mechanical measurements, it appears that the elastic moduli of organic crystals are about the same as those of organic polymers in the glassy state, and that relatively little reinforcement took place under the particular crystallization conditions employed.