Improved interfacial and impact properties of carbon fiber/epoxy composites through grafting hyperbranched polyglycerols on a carbon fiber surface

Grafting hyperbranched polyglycerols onto a carbon fiber surface is done in an attempt to improve the interfacial and impact properties between carbon fiber and epoxy resin. Scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analysis were performed to characterize the carbon fibers. The TGA result shows that the mass fraction of the hyperbranched polyglycerols grafted onto the carbon fibers surface was 9.03%. The SEM results indicate that the hyperbranched polyglycerols have been grafted onto the carbon surface and that the surface roughness of the carbon fiber significantly increased. The XPS result indicates that oxygen-containing functional groups obviously increased after modification. Dynamic contact angle analysis indicates that the surface energy of modified carbon fibers increased significantly compared with the untreated ones. Results of the mechanical property tests show that interfacial shear strength increased from 59.86 to 80.16 MPa, interlaminar shear strength increased from 57.57 to 73.49 MPa and impact strength simultaneously increased from 2.52 to 3.52 J.