Wettability and lubrication of polytetrafluorethylene (PTFE) by UV-induced graft copolymerization on plasma-treated surface

Wettability of PTFE has been investigated by grafting the hydrophilic monomer, acrylamide (AAm). The stable PTFE needs to be activated before grafting. These active sites for further photo-graft polymerization can be provided on the surface of PTFE by an argon plasma (Ar*) or by the introduction of a plasma-deposited HMDSZ layer. Grafting AAm on Ar*-treated PTFE will improve its wettability for theta from 101 to 33 degrees without worsening its low friction coefficient characteristic, about 0.27 for the coefficient of friction against a glass plate in a wet state. Owing to the general characteristics of plasma deposited film, the plasma-deposited HMDSZ layer will provide a smooth substrate with peroxides for further grafting. Therefore, grafting AAm on HMDSZ plasma deposited on PTFE will not only modify the surface from hydrophobic to hydrophilic surface but also reduce the friction coefficient to as low as 0.1.