By the direct radiation grafting technique

effects of hydrochloric acid on radiation induced graft copolymerization have been studied. The experimental results show that the presence of hydrochloric acid markedly enhanced the grafted amount of acrylic acid to polytetrafluoroethyene. From the cross section and surface of the grafted film and its thickness change

it is found that grafting takes place on the surface of poly-tetrofluoroethyene by the presence of hydrochloric acid. The reasons is that the presence of hydrochloric acid will promote existing hydrogen abstraction reactions from the grafted chains to give more grafting sites. The outer-most layer is the homopoly-mer of polyacrylic acid

which is linked by chemical bond with the grafted copolymer

hence its adhesiveness to epoxy resin becomes greater.