Cellulose‐Crosslinked Epoxy Resins/Carbon Nanofiber Hybrid Composites: A Synergistic Study on Strengthening and Toughening Mechanisms

ABSTRACT Cellulose‐crosslinked epoxy resins (TCE, MCE, and HCE) were synthesized through the reaction of cellulose with diglycidyl ether of bisphenol A (EP), employing three diisocyanates with distinct structures as crosslinking agents. The relationship between the structures of crosslinking agents and the properties of the cellulose‐crosslinked epoxy resins was systematically investigated. With 4,4′‐Diaminodiphenylmethane (DDM) as the curing agent, MCE/DDM with a bis‐phenyl structure exhibited superior strength, while HCE/DDM with a long‐chain alkyl structure demonstrated superior toughness. Compared with EP/DDM, HCE/DDM exhibited increases of 127.42%, 70.80%, and 375% in elongation at break, fracture toughness (K _IC ), and critical strain energy release rate (G _IC ), respectively. Moreover, compared to the EP coating, the HCE coating with a long‐chain alkyl structure showed excellent corrosion resistance. Subsequently, MCE/DDM was selected as the resin matrix to prepare corresponding composites (CNF/MCE/DDM), with carbon nanofibers (CNFs). Mechanical testing demonstrated that composites containing 0.5 wt% CNFs exhibited the best overall performance. The strengthening and toughening mechanisms of the resins and composites were explored through a combination of scanning electron microscope (SEM) images and simulated internal networks. This research demonstrated an efficient approach to fabricating high‐performance thermosetting composites through the synergistic utilization of structurally adjustable crosslinkers and CNFs.