Surface modification of polyethylene by radiation‐induced grafting for adhesive bonding. III. Oxidative degradation and stabilization of grafted layer

摘要

AbstractVapor‐phase mutual grafting of methyl acrylate (MA) onto polyethylene (PE) and subsequent saponification treatment produce a surface graft having a high adhesive bondability, which results from the presence of a hydrolized homopolymer layer (consisting of only monomer component) on an inner graft copolymer layer consisting of both PE and monomer components. The oxidative deterioration and the stabilization of the grafted surface layer have been investigated to clarify the long‐term stability of the adhesive bondability. The bondability rapidly disappears with accelerated weathering followed by acetone extraction treatment, whereas it is kept unchanged during thermal‐oxidative aging at 100°C. Microscopic and ATR infrared spectroscopic observations of the degraded surfaces show that the bondability loss is due to degradative removal of the surface homopolymer layer. The addition of combinations of conventional antioxidants and ultraviolet absorbers stabilizes the grafted surface layer against thermal‐oxidative and photo‐oxidative degradation and thus extends the bondability retention time. The stabilization is more effective in the grafts of carbon black‐containing PE, where carbon black is present in the inner‐graft c