Interfacially reinforced unsaturated polyester composites by chemically grafting different functional POSS onto carbon fibers

Monofunctional (methacrylolsobutyl) and multifunctional (methacryl) polyhedral oligomeric silsesquioxane (POSS) were successfully grafted on a carbon fiber (CF) surface to enhance the interfacial strength of CF reinforced unsaturated polyester resin (UPR) composites. The silicon containing functional groups were obviously increased on the CFs after the successful grafting of POSS onto the CF surface. Both kinds of POSS were uniformly grafted on the CF surface and the surface roughness of the CFs grafted with methacryl POSS and methacrylolsobutyl POSS was almost the same (131.6 and 129.6 nm) but much higher than that of the as-received CFs (57.9 nm). Dynamic contact angle analysis of the CFs grafted with both POSS showed almost the same surface energy but higher than that of the as-received CFs. After being grafted with methacrylolsobutyl POSS, the interlaminar shear strength of the composites was 62 MPa, increased by 31.9%, however, in terms of methacryl POSS the value was 67 MPa, increased by 42.6% compared with that of the as-received CFs (47 MPa). The interfacial shear strength (IFSS) of the composites with methacryl POSS grafted CFs (93 MPa) was significantly increased by 102.2% compared with the composites with the as-received CFs (46 MPa) and is even higher than that of the composites with methacrylolsobutyl POSS grafted CFs (87 MPa). The impact energy of 1.72 J for the composites with methacryl POSS grafted CFs is higher than that of the composites with as-received CFs (1.00 J) and methacrylolsobutyl POSS grafted CFs (1.43 J).