Sizing carbon fiber by in situ polymerization of maleic acid and glycerol for reinforcing polyamide 66

Abstract The interfacial adhesion character highly depends on interactions of the interfacial molecules. Carbon fiber (CF) is sized by in situ polymerization of maleic acid and glycerol to form a hyperbranched polyester (HBPE) layer on the surface in an environmental and efficient technique. Vast hydroxyl groups are introduced to the CF surface with the presence of HBPE. Moreover, the HBPE sizing structure on 6 A/m 2 moderately oxidized CF surface presents higher branch extent and more terminal hydroxyl groups than that on unoxidized or over‐oxidized CF surface. The interlaminar shear strength of polyamide 66 composite reinforced with HBPE sized oxidized‐CF under 6 A/m 2 current density is optimal and remarkably enhanced to 77.9 MPa by 46% compared to that with the unsized one. The significant interfacial property improvement is attributed to the abundant terminal hydroxyl groups on HBPE sizing structure, which enhances the interaction at the interface of CF/sizing and sizing/matrix by constructing many covalent and hydrogen bonds.