Modification of cellulose nanocrystals with epoxidized canola oil for enhancing interfacial compatibility with poly(lactic acid)

Herein, we investigate a sustainable hydrophobic modification of cellulose nanocrystals (CNCs) with epoxidized canola oil (ECO) via an oxirane ring-opening reaction, in order to improve compatibility with poly(lactic acid) (PLA). The modified CNCs (CNC-g-ECO) exhibited improved hydrophobicity, as evidenced by their lack of colloidal stability in water and an increase in water contact angle from 33° to 73°. Importantly, XRD analysis indicated that the modification did not disrupt the crystalline structure of the CNCs. Neat and modified CNCs were compounded with PLA at 1 wt% using multiple processing protocols. Polarized optical microscopy revealed that the modified CNCs exhibited significantly improved dispersion and distribution within the PLA matrix across all processing methods. Additionally, the modified CNCs acted as effective nucleating agents for PLA, leading to an increase in its degree of crystallinity. Notably, we found that CNC modification with ECO enhanced thermal stability and completely mitigated discoloration or thermal aging, which is a common occurrence in CNC-based composites, typically caused by CNC degradation and oxidation of carboxyl groups during processing. Overall, our approach gives CNC an expanded thermal processing window and improves dispersion in polymer matrices, facilitating the development of high-performance composites for a number of different applications.