Atomic sulfur generated respectively by the pyrolysis of carbonyl sulfide and by the photolysis of carbonyl sulfide, carbon disulfide, and sulfur vapors has been shown to modify irreversibly the surface of polyethylene as shown by wettability measurements. The nature of the modification is not completely apparent from this portion of the study, however, insertion of the atomic sulfur into a carbon—hydrogen bond to form a surface thiol group appears likely. The modified surfaces thus formed are shown to undergo several classical organic reactions, as determined by wettability measurements.

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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.

synopsisDifluorocarbene (difluoromethylene, : CFZ) generated by the pyrolysis of sodium chlorodifluoroacetate has been shown to irreversibly modify the surfaces of polymers and fibers. The critical surface tension values of several polymers are shown to decrease with increasing exposure to difluorocarbene vapors and ultimately approach the critical surface tension values of partially fluorinated polyethylenes. The rate-controlling step appears to be the diffusion of difluorocarbene from the precursor to the polymer substrate. The nature of the interaction between difluorocarbene and the polymer surface is unknown; however, the absence of infrared bands due to C-F bonds in attenuated total reflection measurements tends to establish the mono-molecular-like character of the modified surface.

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