Solution crystallization of polyethylene at high temperatures

Abstract

Polyethylene single crystals have been grown from solution in a variety of solvents at temperatures up to 120° C. Thus an overlap is achieved with conditions used for melt growth in terms of both absolute crystallization temperature (T _c) and supercooling (ΔT). Interesting developments in two-dimensional crystal habits, including the increase in axial ratio and curvature of lateral crystal faces (lamellar prism faces), have been examined and quantified. The crystal habit is found to depend primarily onT _c, regardless of solvent, although some ΔT dependence is indicated within a series of similar solvents. AsT _c is raised the {1 0 0} crystal faces become increasingly curved and the {1 1 0} faces also begin to exhibit a slight curvature. The implications of these morphological developments for theories of polymer crystallization are discussed and the justification of new approaches embodying also the lateral habit features, at least in the extendedT _c ranges considered here, is indicated. Also, similarities with crystals grown under similar conditions from the melt are noted.