Rosin-Modified Microcrystalline Cellulose for Enhancing Polylactic Acid-Based Composites with Good Interfacial Compatibility and Mechanical Performance

The interfacial incompatibility and insufficient mechanical performance of polylactic acid (PLA)/cellulose composites have severely restricted their practical applications. To address the critical issue of interfacial incompatibility in PLA/cellulose composites, this work developed a novel strategy employing rosin emulsion for blending modification of microcrystalline cellulose (MCC), followed by a one-step extrusion process to fabricate PLA composites. The corresponding analyses confirmed that the rosin has been successfully added to MCC surfaces, forming the hydrophobic interface while maintaining the cellulose I crystalline structure. Subsequently, rosin emulsion-modified MCC (MCC-R) reinforced PLA (PLA/MCC-R) composites were fabricated via twin-screw extrusion at varying MCC-R contents. The testing results illustrated that the introduction of 8 wt% MCC-R can enhance the mechanical properties of PLA/MCC-R composites with the flexural strength (125.5 MPa), tensile strength (30.8 MPa), Young's modulus (1.19 GPa), and elongation at break (3.07%), which was attributed to enhanced filler dispersion and interfacial stress transfer. Overall, this work established a facile and sustainable strategy for developing multifunctional PLA composites with engineered interfaces and mechanical robustness, which is vital for practical application. The as-prepared PLA composites show promising application prospects in environmentally friendly packaging, biodegradable disposable products, and lightweight structural components.