α_c Relaxation of the constrained amorphous phase

Abstract

The study presents properties of polyethylene commercial products with special attention to properties of a ‘semi-ordered’ amorphous phase. Although, one can hardly prove the existence of such an interphase, the results description based on the idea of coexistence of two amorphous fractions (‘real’ and ‘semi-ordered’) in one system gives a broader understanding of the relationship between product history and morphology of the resultant engineering products. Their supermolecular structures were explored using positron annihilation lifetime spectroscopy (PALS), calorimetry (DSC) and mechanical spectroscopy in a tensile and a torsion mode (DMTA). The stability of these structures is also discussed based on a simple statistical analysis of the thermodynamic and structural parameters. The study exhibited that chalk did not disturb too much the crystalline domains of PE-LD whereas it influenced the interphase. Mechanical study showed that such a product is not stable during long time storage. The comparison with previous results, obtained for PE-carbon black composites, revealed differences in the morphologies and the α_c relaxations of PE chains, observed in the composites including various fillers.