Effect of Plasma Treatment on the Adhesion of Carbon Fibers to Thermoplastic Polymers

A study has been made of the effect of RF plasmas on the adhesion of carbon fibers to polycarbonate and polysulfone. Treatment in oxygen plasma significantly increased the adhesion to both polymers. The effect is lost if the treated fiber is stored in air for a week. Surface analysis using XPS indicated an increase in atom percent oxygen but the spectra were unchanged for the stored fibers even though there had been a significant loss in adhesion. It is suggested that oxygen surface functionality is responsible for the improved adhesion but that this surface activation is lost on storage. Due to a sampling depth of 5-10 nm, XPS would not be expected to detect this small change in surface functionality.