Photoinitiated crosslinking polyethylene studied by positron annihilation technique

The effects of crosslinking degree, crystalline degree, branching degree of the ultraviolet-photoinitiated crosslinking polyethylene ( UPCP ) were studied by the positron annihilation lifetime spectroscopy. During the polyethylene’s crosslinking initiated by high energy radiation, I3 decreases when the crosslinking degree of polyethylene increases, but the ultraviolet-photoinitiated crosslinking polyethylene’s I3 increases when its crosslinking degree increases in our experiment, and the trend of I3 is the same as that of its crosslinking degree. This can be attributed to the fact that the increase of UPCP’s crosslinking degree makes its crystal degree decrease, and as the initiator in the photocrosslinking of polyethylene attracts the ultraviolet-photons, its polar carbonyl groups which can attract electrons strongly transform into the weakly attracting electrons’ polar hydroxyl groups.