Surface modification of microcrystalline cellulose using rice bran oil: a bio-based approach to achieve water repellency

Abstract

A bio-based approach for surface modification of microcrystalline cellulose (MCC) with hydrophobic property was achieved by chemical transesterification using rice bran oil (RBO) as a cheap and environmentally benign raw material. The pretreated MCC (UMCC) was uniformly distributed in a homogeneous mixture of RBO/ethanol emulsion. Surface acylation was enabled by solvent evaporation followed by heating. Acylation of UMCC (AUMCC) was analyzed by 13C NMR, FTIR and acid-base titrations. Average acylation by titration method for AUMCC with 2 mL RBO at 110 °C for 30, 60, and 90 min was found to be 11.05, 13.26 and 15.39%, respectively. The stoichiometric and mass yield of AUMCC was found to be 80.9 and ~70% respectively. 13C solid-state NMR study proved the modification of UMCC. Percentage acylation by solid-state NMR was found to be 13.94% which is slightly lower than the average acylation by titration method i.e. 15.39%. The solubility of AUMCC in common organic solvents was examined and found to be soluble in pyridine and benzene solvent. The water contact angle of AUMCC reached 92.2°, while the surface energy decreasing to 35.56 mN/m, and water uptake of 0.9 mL/mg was achieved. The thermal stability and crystallinity of AUMCC decreased with treatment time. The functionalization of these AUMCC can be useful in the preparation of composites.