Long chain alkyl grafted cellulose and PBST synergistically reinforce PLA: Balanced strength, toughness, and barrier properties.

Poly(lactic acid) (PLA) is a promising biodegradable polymer, yet its inherent brittleness, poor barrier properties, and slow crystallization rate limit its application in food packaging. In this study, hydrophobically modified microcrystalline cellulose (eMCC) and poly(butylene succinate-co-terephthalate) (PBST) were incorporated into PLA via solution casting to prepare a ternary composite with balanced properties. Characterization by polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry demonstrated that eMCC promoted heterogeneous nucleation of PLA under isothermal conditions, while PBST served as a ductile toughening phase. Owing to synergistic interfacial interactions, primarily hydrogen bonding and van der Waals forces, eMCC was uniformly dispersed and exhibited strong interfacial adhesion with both polymer phases. The resulting composite achieved a tensile strength of 39.7 MPa while retaining a high elongation at break of 199.9%, reflecting a favorable balance between stiffness and toughness. Barrier property measurements revealed that the water vapor and oxygen barrier properties were improved by 18.0% and 26.1%, respectively, compared with neat PLA. This work provides an effective strategy for utilizing hydrophobically modified microcrystalline cellulose to develop food packaging materials with high performance and potential biodegradability.