Strategies for the enhancement of adhesion between carbon fibers and polyolefin matrices

Carbon fiber reinforced polyolefin (polyethylene, polypropylene, etc.) composites would be attractive materials for many applications, including aquatic sporting equipment, if fiber-matrix adhesion could be brought to acceptable levels. The present work explores a variety of strategies for adhesion promotion in these types of systems. The use of conventional (silane) and unconventional (titanate and zirconate) coupling agents, matrix additives, surface treatments producing interphase modulus graduation, and combinations of the above is examined using fiber pullout tests for T700 GC-12k-91 carbon fibers embedded in both polyethylene and polypropylene matrices. Only modest enhancements were achieved in all cases using coupling agents and other surface treatments, with azidosulfonyl silanes producing interfacial shear strengths (IFSS) to levels approaching 15 MPa for low density polyethylene (LDPE). The use of maleic anhydride graft copolymer matrix additives achieved similar results. The combination of azidosulfonyl silane surface treatment with maleic anhydride additive produced IFSS values approaching 30 MPa.