Grafting of acrylamide and acrylic acid onto polyethylene fiber for improved adhesion to epoxy resin

Surface modification of polyethylene (PE) fiber via 2-stage grafting to improve its adhesion to epoxy resin was studied. The PE fiber was first functionalized by thermal decomposition of potassium peroxydisulfate to create grafting sites. In the second stage, functionalized fiber was grafted with acrylamide (AAm) and acrylic acid (AAc) monomer by Ceric (IV) ion technique. The adhesion of grafted fibers to epoxy resin was studied by a single fiber pull out test. Pull out strength increases about 2 folds after functionalization and 3.5 and 4.8 folds after grafting with AAm and AAc, respectively. The improvement in pull out strength after functionalization and grafting are due to physical interaction and the formation of chemical bonding, respectively. Traces of transfering materials on the surface of pulled out fiber suggested that failure could be due to cohesive failure of either epoxy resin or grafted layer. Preliminary study of surface grafted fiber/epoxy composite showed significant improvement in flexural and impact strength over unreinforced resin and untreated fiber reinforced composite.