CHEMICAL PROCESSES IN THE CROSS-LINKING OF POLYETHYLENE

The chemistry of the reactions proceeding in the cross-linking of polyethylene by procedures which are presently used on an industrial scale is described. The initiation of the process with a peroxide belong here in the first place, and not only in the original thermic form, but in its newer modification, either under the effect of high pressure, or an electromagnetic field with an ultrahigh frequency, or even an oxidation-reduction reaction. In addition to the peroxide cross-linking with several possibilities, a further alternative of thermic iniciation is mentioned, involving azo-compounds. This survey is completed by the chemical aspects of the cross-linking reactions of the polymer below the temperature of its melting, under the application of silanes or ionizing radiation.