Improvement of interfacial adhesion of poly(m-phenylene isophthalamide) short fiber-thermoplastic elastomer (SEBS) composites by N-alkylation on fiber surface

A composite of short-fiber, poly(m-phenylene isophthalamide), and thermoplastic elastomer styrene (ethylene–butylene) styrene (SEBS), was investigated. The fiber surface was modified by N-alkylation (heptylation and dodecylation) to improve their compatibility with a less polar SEBS matrix. Observation of fiber-surface morphology by SEM revealed surface roughness after N-alkylation. Nearly complete coating of the polymer matrix on the fiber was observed on a fractured surface of the composite, which is evidence for the improvement of fiber–matrix adhesion. It was found that the modulus of the composites grew with increasing fiber loading to approximately the same extent for both unmodified and modified fiber composites. Tensile strength of the modified fiber composites was found to improve significantly over that of the unmodified fiber composite. This suggests that the presence of the alkyl group on the fiber surface is responsible for an improvement of interfacial adhesion.