Gel-sol analysis of the effect of electron beam irradiation on the macromolecular structure and crosslinking parameters in low density polyethylene films

The effect of electron beam irradiation with different current intensities on the macromolecular structure and crosslinking parameters in low density polyethylene films (LDPE) has been studied. The electron beam irradiation leads to the creation of regions with strong polymer's own elastification without using external elastificators. At the same time new crystalline regions with straight chains in the intercrystalline amorphous regions are created. The sol fraction (Ws) and the dependence Ws + Ws1/2 = f (1/D) have different behaviour at irradiation with Ic = 1 mA and Ic = 2 mA. The ratio G(Y)/2G(X), which gives the intensity of the crosslinking and of the destruction processes, is quite different for the different current intensities and in the different dose intervals. The change of the density of the crosslinking of the macromolecular chains (υc) and of the number-average molecular weight of the macromolecular segments of the three dimensional network (< Mn, c) is monotonical at irradiation with Ic = 1 mA, but at irradiation with Ic = 2 mA the same quantities show extremes at dose 16 Mrad. Although the behaviour of (υc) and (< Mn, C) is different for the different current intensities, the dependence (υc) = f (< Mn, C) does not depend on the current intensity. These processes and their competing contributions in obtaining the new macromolecular structures enable the obtaining of various programmable changes in polymer properties even at one and the same irradiation dose. (author)