Surface and bulk properties of polyethylene single crystals

Abstract

Enthalpies of fusion in the range –35°C → melting point have been measured for polyethylene single crystals grown at 70, 80 and 90°C. Rates of heating in adiabatic calorimetry are slow and irreversible annealing effects contribute to the apparent entropy of fusion. Reasonable corrections, reproducing the observed melting points in rapid heating experiments, are discussed and the morphological implications of the resulting surface free energies and enthalpies considered. A defected (but not completely amorphous) surface structure is most consistent with the observations.