Matrix‐Homologous Polyketone Sizing for Interface Engineering of Basalt Fiber/Polyketone Composites

ABSTRACT Interfacial incompatibility between inorganic basalt fiber and polyketone limits load transfer in basalt fiber/polyketone composites. A matrix‐homologous waterborne sizing was therefore prepared by partially functionalizing polyketone with an amino alcohol through Paal–Knorr chemistry, followed by protonation‐induced phase inversion. The retained polyketone backbone promoted compatibility with the matrix, whereas amine and hydroxyl groups improved aqueous processing and fiber‐side interactions. Basalt fibers were first treated with epoxy‐functional γ‐glycidoxypropyltrimethoxysilane and then coated with the modified polyketone. Spectroscopic and microscopic analyses verified a nitrogen‐containing organic interphase anchored to the fiber surface. Moderate functionalization produced the most continuous coating while limiting aggregation and thermal‐stability loss. The optimal intermediate treatment increased interfacial shear strength from 7.657 to 15.065 MPa (96.7%) and arithmetic mean single‐filament tensile strength from 1.327 to 1.523 GPa (14.8%). Debonded fibers retained more resin, and the failure mode shifted from clean interfacial debonding to mixed interfacial/cohesive failure. The results demonstrate that fiber‐side silane anchoring, defect passivation, polar interactions, and matrix‐side chain interdiffusion jointly form an effective load‐transfer interphase. This waterborne, matrix‐derived sizing strategy provides a practical route to strengthening basalt fiber/polyketone thermoplastic composites.