SURFACE MODIFICATION OF FLUOROCARBON POLYMERS BY RADIATION-INDUCED GRAFTING FOR ADHESIVE BONDING

The mutual irradiation of polymers in methyl acrylate (MA) vapor followed by hydrolysis treatment is a surface grafting technique which had been developed originally for surface modification of polyethylene (PE). The technique now has been successfully applied to surface modification of two radiation-degradative fluorocarbon polymers, poly(tetrafluoroethylene) (PTFE) and poly(chlorotrifluoroethylene) (PCTFE). The adhesive bond strengths reach a maximum value when the grafted surface is covered with an outer homopolymer layer consisting only of the monomer component. Although this relationship between bond strength and homopolymer surface coincides with that suggested in PE grafts, it is shown more clearly by ESCA analysis of the modified fluoropolymer surfaces. The thickness of the homopolymer layer passes through a maximum and then decreases with irradiation time or dose. This decrease may reflect the radiation degradation of fluoropolymer chains. The peel strengths of grafted PTFE sheets are much higher than those of sodium (Na)-etched PTFE sheets. This difference in bond improvement is discussed in terms of mechanical strength of the modified surface layers. © 1979, American Chemical Society. All rights reserved.