Lipase-catalyzed laurate esterification of cellulose nanocrystals and their use as reinforcement in PLA composites

• Published in: Cellulose (London) Vol. 27; no. 11; pp. 6263 - 6273
• Main Authors: Yin, Yuanyuan, Lucia, Lucian A., Pal, Lokendra, Jiang, Xue, Hubbe, Martin A.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.07.2020; Springer Nature B.V
• Subjects: Bioorganic Chemistry; Breakage; Cellulose; Cellulose esters; Ceramics; Chemistry; Chemistry and Materials Science; Composites; Contact angle; Crystallization; Dispersion; Elongation; Esterification; Glass; Hydrophobicity; Lipase; Mechanical properties; Nanocrystals; Natural Materials; NMR; Nuclear magnetic resonance; Organic Chemistry; Original Research; Photomicrographs; Physical Chemistry; Polylactic acid; Polymer Sciences; Structural stability; Sustainable Development; Tensile strength; Mechanical properties; Lipase; Cellulose nanocrystals; PLA biocomposites
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1007/s10570-020-03225-3

Cellulose nanocrystals (CNCs) were surface-modified using immobilized lipase (Novozyme 435) to catalyze the formation of laurate ester groups on the CNC surface and thus facilitate homogeneous dispersion within a poly(lactic acid) (PLA) matrix. Results of dynamic contact angle measurement revealed that the modified CNCs (CNC-LAA) presented greater hydrophobicity than their CNC controls. FT-IR, 13 C-NMR, XRD, and TGA were used to characterize the structure and stability of the CNCs before and after modification. PLA reinforced with the modified CNCs were prepared, and the effect on mechanical properties was studied. SEM micrographs suggested uniform dispersion of modified CNCs throughout the PLA matrix at a maximum 1 wt% loading, which was found to be the optimal loading level. The CNC-LAA were able to achieve a 0.4 maximum degree of substitution. DSC indicated enhanced crystallization of PLA chains due to the inclusion of CNC-LAA, indicating that the nanofillers behaved as nucleating agents and also revealed improved compatibility. Tensile strength tests showed slightly improved mechanical properties for breaking strength and elongation at breakage.