| The changes of micro structure and macro properties of polyethylene during grafting process were investigated by means of infra-red spectrum analysis and molecular weight and cross-linking rate and flow rate index testing in this paper. The effects of polyethylene resin, silane structure, grafting agent and activator on the properties of XLPE products were investigated also. The results of experiments showed: (1) in the process of grafting the reactions of hydrolytic condensation among the silane grafted polyethylene molecular chain occurred, polyethylene molecular weight significantly increased, melt flow rate evidently decreased; (2) the polyethylene contained more and longer branch chains could easily get greater grafting rate and the degree of cross-linking and the density of cross-linking, but the properties of manufacturability would be worse; (3) the silane contained smaller molecular weight and greater activity would get higher grafting rate and hydrolytic condensation reaction rate, meanwhile the cable material got greater degree of cross-linking, the probability of pre-cross-link would increase; (4) in a specific range, through increasing the dose of activator, the degree of cross-linking could increase, but too much activator would cause increasing of C-C link among polyethylene and decreasing of manufacturability of cable material; (5) too much grafting agent could cause hyper-cross-link, and sharp decrease of tensile strength and elongation rate of rupture. Based on the above investigations, the formula and production process of solid phase monosile silane cross-linking polyethylene cable insulating compounds were developed. |
