Preparation of Polyethylene Wax Sizing Agent and Its Application in Carbon Fiber Reinforced Polyethylene Composites

Carbon fiber reinforced polyethylene (CF/PE) composites are widely used in aerospace, automotive, and sports equipment applications. The interphase acts as the critical bridge for stress transfer. However, the carbon fiber surface is nonpolar and smooth and lacks reactive functional groups, while the polyethylene molecular chains also contain no reactive groups. This leads to weak interfacial bonding between the fibers and the matrix. A weak interface easily undergoes debonding, leading to internal crack formation and severely limiting the overall mechanical performance of the composites. Herein, a polyethylene wax (PEW)-derived sizing agent functionalized with maleic anhydride (MAH) was applied onto carbon fiber surfaces via aqueous coating to construct an interfacial transition layer, thereby enhancing the interfacial adhesion in CF/PE composites. Successful sizing was verified by x-ray photoelectron spectroscopy (XPS). The tensile and impact strengths of the modified CF/PE composites were enhanced by 73.2% and 20.0%, respectively; the interfacial shear strength (IFSS) improved from 5.43 to 18.45 MPa; and the interlaminar shear strength (ILSS) increased from 53.47 MPa for untreated CF/PE composites to 63.27 MPa. The results indicate that the compatibilizer, based on similar compatibility and esterification effects, improved the interfacial adhesion of the composites. Highlights Reactive PE wax sizing agent with maleic anhydride groups was prepared. Robust interfacial adhesion between CF and PE via chemical surface modification. Poor compatibility between conventional epoxy sizes and polyolefins was overcome.