Gallic acid and poly(propylene glycol) diglycidyl ether (PPGDGE)-co-modified sugarcane fiber/PLA composites with enhanced strength and toughness

To address global plastic pollution and other issues, the development of biodegradable disposable products to replace petroleum-based plastics is urgent. In this study, a fully bio-based sugarcane fiber (SF)/polylactic acid (PLA) composite was developed for potential applications in biodegradable disposable tableware, packaging, and other related fields. We melt-blended gallic acid (GA) as an interfacial crosslinker with SF/PLA to form a hydrogen bond network at the SF and PLA interfaces to improve the interfacial strength of the composite materials. Subsequently, polypropylene glycol diglycidyl ether (PPGDGE) was introduced as a reactive compatibilizer to introduce flexible segments and construct localized cross-linked networks within the composite. The resulting SF/GA/PLA/PPGDGE composite exhibited an impact strength of 9.67 ± 0.59 kJ/m 2 and a tensile strength of 44.97 ± 1.59 MPa, representing increases of 89.61% and 49.11%, respectively, compared with the SF/PLA composite. The elongation at break rose from 5.06% to 10.9%, corresponding to an increase of approximately 2.15 times. However, with the introduction of PPGDGE, the thermal stability of composite materials may decrease. Contact angle testing demonstrates improved water resistance of composite materials. after 10 s, the contact angle increased from 69.17° for SF/PLA to 91.7° for SF/GA/PLA/PPGDGE, indicating better hydrophobic stability of the SF/GA/PLA/PPGDGE composite. These enhancements in mechanical performance and water resistance were mainly due to the synergistic effects of GA-induced interfacial hydrogen bonding and PPGDGE-driven localized crosslinking, which together improved stress transfer efficiency and energy dissipation within the composite. Overall, this study provides an effective strategy for interfacial modification and for achieving a balance between strength and toughness in plant fiber/PLA composites, with the resulting material showing strong potential for biodegradable disposable tableware, packaging, and other single-use applications.