A Novel Approach to Toughening Epoxy and Its Glass Fiber Composite System Using Biodegradable Polybutylene Adipate‐Co‐Terephthalate

ABSTRACT This study explores a novel toughening strategy for epoxy (EP) through incorporation of poly (butylene adipate‐co‐terephthalate) (PBAT). At the optimum PBAT content of 4 wt.% (EP/PBAT), the tensile strength, mode‐I fracture toughness, and impact strength increased by 47%, 64%, and 135%, respectively, compared with neat EP. These improvements are attributed to PBAT particle cavitation and plastic void growth, which promote enhanced energy dissipation. Fourier transform infrared spectroscopy (FTIR) revealed no additional chemical interactions or specific intermolecular interactions between two phases, indicating that toughening primarily originated from physical mechanisms associated with phase separation. Linear elastic fracture mechanics (LEFM) was employed to understand crack propagation behavior. To assess structural applications, chopped strand mat (CSM) glass fibers (GFs) were incorporated into neat EP and optimized blend to fabricate GF composites. Compared to EP‐GF, the modified composites exhibited increases of 39%, 8%, 40%, and 20% in fracture toughness, impact strength, apparent short beam shear stress, and tensile strength, respectively. Scanning electron microscopy (SEM) revealed phase dispersion and fracture mechanisms, while differential scanning calorimetry (DSC) indicated delayed gelation in the optimal blend system. Overall, PBAT effectively toughens EP, while GF reinforcement provides synergistic structural performance.