Surface modification of polytetrafluoroethylene films by plasma pretreatment and graft copolymerization to improve their adhesion to bismaleimide

BACKGROUND: Polytetrafluoroethylene (PTFE) is utilized in many engineering applications, but its poor wettability and adhesion properties with other materials have limited its use. The study reported was aimed at achieving surface modification of PTFE films by radiofrequency NH₃ and N₂ plasma treatment, followed by graft copolymerization, in order to improve the interfacial adhesion of PTFE and bismaleimide. RESULTS: X‐ray photoelectron spectroscopy results showed that a short‐time plasma treatment had a distinct defluorination effect and led to nitrogen functional group formation. The nitrogen chemical bonding form was different for NH₃ and N₂ plasma treatments. Under the same experimental conditions, the NH₃ plasma exhibited a better etching effect than did the N₂ plasma. Contact angle measurement showed an improvement in both surface energy and wettabliity by short‐time plasma treatment. The concentration of the surface‐grafted bismaleimide on PTFE increased after the plasma pretreatment. The lap shear strength between PTFE and bismaleimide increased significantly after surface modification. CONCLUSION: This study found that plasma treatment caused changes in surface chemistry, thus leading to an increase of the wettability of PTFE surfaces. Hence, the adhesion properties of PTFE with bismaleimide were significantly improved. Copyright © 2008 Society of Chemical Industry