Compatibilization and Plasticization of Poly(Lactic Acid) by Eco-Friendly Castor Oil-Based Plasticizers

To address the inherent brittleness of polylactic acid (PLA) that restricts its application in flexible packaging and to avoid the drawbacks of petroleum-based plasticizers such as toxic residues and non-biodegradability, PLA/castor oil (CO)/castor oil glycidyl ether (COGE) blends were prepared via one-step melt blending method. The results indicated that CO and COGE was compatible and both showed good affinity with PLA, thus multiple intermolecular hydrogen bonds were formed among three components, effectively improving the movability of PLA chains. COGE not only significantly improved the dispersion of CO in the PLA matrix and reduced the size of dispersed phases, but also enhanced the interfacial adhesion of the blends through its ring-opening reaction with PLA. Due to the enhanced mobility of molecular chains, the glass transition temperature decreased, the crystallinity slightly increased, and the melt viscosity of the blends significantly decreased. The elongation at break of the PLA/CO/COGE (85/6/9) blend reached 176.24%, which was 18 times greater than that of pure PLA, meanwhile, the Young’s modulus decreased by less than 15%, demonstrating a balance between high rigidity and preferable ductility. This synergistic plasticizing strategy provides a practical approach for the development of flexible PLA materials for biodegradable packaging and disposable products.

为解决聚乳酸（PLA）固有脆性限制其在柔性包装领域应用的问题，同时规避石油基增塑剂存在的有毒残留、不可生物降解等缺陷，研究人员采用一步熔融共混法制备了PLA/蓖麻油（CO）/蓖麻油缩水甘油醚（COGE）共混物。结果表明，CO与COGE相容性良好，且二者均与PLA表现出优异的亲和性，因此三种组分间形成了多重分子间氢键，有效提升了PLA分子链的运动能力。COGE不仅显著改善了CO在PLA基体中的分散性、减小了分散相尺寸，还可通过与PLA的开环反应增强共混物的界面黏附力。得益于分子链运动能力的提升，共混物的玻璃化转变温度降低，结晶度小幅升高，熔体黏度则显著下降。PLA/CO/COGE（85/6/9）共混物的断裂伸长率可达176.24%，为纯PLA的18倍；与此同时其杨氏模量降幅不足15%，实现了高刚性与优良延展性的平衡。该协同增塑策略为可生物降解包装及一次性制品用柔性PLA材料的开发提供了切实可行的途径。