Density, energy and entropy of defects in the crystalline regions of crosslinked polyethylene)

Abstract

By comparison of small angle X-ray scattering, thermal analytical and electron microscopic investigations, it is shown that crosslinked polyethylene crystallizes according to the usual folded chain scheme up to defect densities of 0.9 % and crystallizes micellarly for higher ones. The energy needed for the insertion of a crosslink into the lattice was estimated to be 3.3 eV, indicating a strong deterioration of the crystal. Similarly, the calculated entropy change due to crosslinks in the crystalline regions, 7 meV/K per crosslink, is rather high. This value an be explained by assuming that crosslinks are incorporated into the crystals in a variety of conformational and configurational different ways.