RADIATION-INDUCED CROSS-LINKING OF POLYETHYLENE IN THE PRESENCE OF ACETYLENE - A GEL FRACTION, UV-VISIBLE, AND ESR SPECTROSCOPY STUDY

Electron-spin resonance (ESR) and ultraviolet (UV) visible spectroscop ic evidence has been found for the formation of diene, triene and tetr aene, following the irradiation of polyethylene in the presence of ace tylene. The polyenes are formed by a mechanism which is different from that observed under vacuum or with inert gas saturation. The sum of t he G(polyene) values obtained by UV spectroscopy is almost half that o f initial radical formation. It is concluded that polyene bridges, pre dominantly diene, form crosslinks between radical pairs. G(X) values d etermined from gel fraction data, using Saito-Kang-Dole theory, are fo und to be greatly in error and misrepresentative of crosslink changes.