Some studies of the crystallization of polychlorotrifluoroethylene copolymer films

A fluorocarbon copolymer of chlorotrifluoroethylene (96%) and vinylidene fluoride has been isothermally crystallized and the quenched films analyzed by the light microscope, photographic light‐scattering, and density measurements. Above a supercooling of 79°C., homogeneous nucleation dominates, giving a morphology that appears to be that of a twisted ribbon. At supercoolings below 79°C., heterogeneous nucleation dominates and leads to spherulitic morphology. Sheaf or rodlike morphology occurs at very low supercoolings. Crystallization rates determined from density measurements at room temperature indicate maximum rate due to heterogeneous nucleation occurring at a supercooling greater than 79°C., but the temperature for maximum rate cannot be identified because of the transition to homogeneous nucleation which causes a discontinuity in the rate versus temperature curve. Superposability of crystallization isotherms constructed from density values are inconsistent with the large melting point lowering from that of polychlorotrifluoroethylene for this copolymer. However, this may be explained by the presence of a different crystal system for each monomer in the copolymer.