Fully Bio-Based Composites of Poly (Lactic Acid) Reinforced with Cellulose-Graft-Poly-(ε-Caprolactone) Copolymers
Chengtao Gao, Yang Wu, Haibo Xie
Abstract
Due to the increasing demand for modified polylactide (PLA) meeting “double green” criteria, the research on sustainable plasticizers for PLA has attracted broad attentions. This study reported an open-ring polymerization method to fabricate cellulose (MCC)-g-PCL (poly (ε-caprolactone)) copolymers with a fully sustainable and biodegradable component. MCC-g-PCL copolymers were synthesized, characterized, and used as green plasticizers for the PLA toughening. The results indicated that the MCC-g-PCL derivatives play an important role in the compatibility, crystallization, and toughening of the PLA/MCC-g-PCL composites. The mechanical properties of the fully bio-based PLA/MCC-g-PCL composites were optimized by adding 15 wt% MCC-g-PCL, that is, the elongation at break was 22.6% (~376% higher than that of neat PLA), the tensile strength was 47.3 MPa (comparable to that of neat PLA), and the impact strength was 26 J/m (~130% higher than that of neat PLA). DSC results indicated that MCC-g-PCL reduced the Tg of the PLA blend. When the addition amount was 15 wt%, the Tg of the blend was 58.4°C. Compared with MCC, MCC-g-PCL polyester plasticizer has better thermal stability, T5% (°C) can still be maintained above 300°C. The rheological results showed that MCC-g-PCL acted as a plasticizer, the introduction of PCL flexible chain increased the mobility of PLA molecular chain, and decreased the complex viscosity, storage modulus and loss modulus of PLA blends. The MCC-g-PCL derivatives, as a new green plastic additive, have shown an interesting prospect to prepare fully bio-based composites.