Improving the Wettability of Deep-Groove Polypropylene Fibers by Photografting

This paper presented photografting as a surface modification method to provide permanent wettability improvement to deep-groove polypropylene (PP) fibers. We also evaluated their wettability by testing the dynamic contact angle (DCA) on single fibers and characterized the wicking performance of fiber bundles when polyacrylamide (PAAm) and polyacrylic acid (PAA) were grafted onto the fibers. In this study, the increase in monomer concentration was found more effective than longer UV exposure time in creating higher graft density on deep-groove PP fibers. Acrylic acid (AA) monomers penetrated into the fiber and polymerized inside, but acrylamide (AAm) did not. Fiber dimension changed slightly upon grafting of PAAm, and enlarged significantly after grafting with PAA. DCA results show that the advancing water contact angle on single fibers decreased from 1.00 to 55 degrees by grafting of PAAm and PAA, and spontaneous wicking of water was observed after surface modification. The wicking amount of the vertically placed fiber bundles showed a linear relationship to the square root of time at early wicking times.