Analysis of the α-relaxation process of bulk crystallized polyethylene based on that of single crystal mat

Abstract

A new concept of the nature of the α₁-relaxation mechanism of high-density polyethylene is proposed. This concept is based on the mechanical properties observed in the α-temperature range for as-grown single crystal mats and for samples of bulk crystallized material. The decomposition of the α-multiple-relaxation process into separate α₁ and α₂-processes was carried out using several different assumptions. These were based on the magnitude of activation energy, on the absorption curve profile of the α₂-mechanism, and on the morphological aspects of hollow pyramidal single crystal and lamellar platelets. Based on the paracrystalline analysis proposed by Hosemann, it is suggested that the lamellar platelets of bulk spherulites are composed of a mosaic block structure. These mosaic blocks have diameters of 130∼180 Å, heights of 170∼400 Å, and intermosaic block distances of several angstroms with specific values depending upon the annealing temperature. The magnitude of the energy dissipation produced by deformation in the intermosaic block region has been evaluated using the magnitudes of the mosaic block core, the long period, and the viscosity of the intermosaic block region. Based on both the model calculation of energy dissipation and on the morphological analysis of the mosaic block structure, it is considered that deformation of the intermosaic block region and interlamellar slip are both possible origins of the α₁-relaxation mechanism. The nature of the α₂-relaxation process is discussed from the view-point of the absorption magnitude of the α₂-peak, the location of its peak temperature, and the thickness of the mosaic block crystalline core.