Effect of surface properties and sizing agents on interfacial properties of carbon fiber reinforced polycarbonate composites

Carbon fiber (CF)/polycarbonate composites were prepared by the same method using five different CFs. Two different PAN-based CFs were supplied by Jiangsu Hengsheng Carbon Fibers Inc. Both had been prepared under the same conditions but one had been anodically oxidized and sized with epoxy. The raw fiber (#1) was subjected to three treatments in our lab:(#2) anodic oxidation, (#3) anodic oxidation followed by sizing with polyurethane, and (#4) anodic oxidation followed by sizing with epoxy. The fiber that had been anodically oxidized and sized with epoxy by the manufacturer is designated #5. The surface functional groups, wettability and interlaminar shear strength (ILSS) of the five CFs composited with polycarbonate were investigated and compared. Results indicate that the smallest number of active groups exists on the #1 CFs, their wettability by polycarbonate is the worst and the ILSS of the composite is the lowest (38.1 MPa). The number of active groups on the #2 CFs is greatly increased, their wettability by polycarbonate is improved and the ILSS is increased to 50.6 MPa much higher that that of the composite with #1 CFs. The number of active groups on the #5 CFs is much higher than on the #2 CFs and their wettability is much better, but the ILSS of their composite is the same as that with the #2 CFs. The ILSS of the composite prepared using the #4 CFs is lower (about 31.7-39.5 MPa) than that with the #3 CFs. The number of the active groups on the #3 CFs and their wettability by polycarbonate are comparable to those of the #5 CFs, but their ILSS (60.4 MPa) greater by 18.9%, which is ascribed to the strong interactions between the polyurethane, the CF surface and the polycarbonate.