Investigations of the nature of the crystallinity degree variations in polyethylene after thermomagnetic treatment (TMT)

The results from initial experiments are presented on the alterations of the crystalline level in the high-density polyethylene (ρ=954 kg/cm, coefficient of polymerization 700000) under TMT regime. Treated samples with a good reiteration of the physical properties are prepared, which is prooved by the good correlation between their characteristics: density, diamond hardness, cristallinity degree and half-width of the crystallographic reflex. A good coincidence between the measured and calculated density is found. It is concluded that the changes of the X-ray crystallinity degree are due to the changes in the boundary layer between the crystalline and the amorphous phases. It is proved that X-ray cristallinity can not be considered as a volumetric increase of the crystallities. The widening of the diffractions lines may be connected with the presence of defects, deformations or internal strains in the overmolecular structure of the polymer system. For their estimations it is necessary to use the Hosemann's method. 5 figs.; 2 tabs.; 12 refs