Sulfur modification of polyethylene surfaces. II. Modification of polyethylene surfaces with fuming sulfuric acid

Previous work has shown that atomic sulfur irreversibility modifies polyethylene, presumably through an insertion reaction into carbon—hydrogen bonds with formation of surface thiol groups. The thiol groups were then oxidized to sulfonic acid surface groups, which were further reacted chemically as shown by wettability measurements. In this work the thiol group was bypassed and the surface sulfonic acid groups were obtained by exposing the polyethylene surface directly to fuming sulfuric acid. The sulfonic acid groups were reacted further. Critical surface tension values identical with those in the previous work with atomic sulfur were obtained, thus substantiating the previous work.