Characteristics of cellulose nanofibril films prepared by liquid- and gas-phase esterification processes

Abstract

Cellulose nanofibrils (CNFs) are versatile materials, but their sensitivity to humidity affects performance. Esterification with fatty acids enhances the hydrophobicity of CNF films. This study compared gas- and liquid-phase esterification using three fatty acid chlorides at different dosages. Gas-phase esterification minimally affected cellulose crystallinity, maintaining a crystallinity index exceeding 55.8%, whereas liquid-phase esterification significantly reduced crystallinity. Gas-phase esterification achieved hydrophobicity (water contact angle >100°) with less fatty acid chlorides (0.50 eq/OH) compared to liquid-phase esterification (1.00 eq/OH). Tensile strength significantly dropped in the liquid phase (68.4–6 MPa) and up to an 8-fold decrease in the elastic modulus. Conversely, gas-phase esterification maintained tensile strength over 40 MPa, and elastic modulus increased by a minimum of 2.5 times. However, gas-phase esterification resulted in a 5-fold reduction in elongation at break (%). Thermogravimetric analysis indicated a high T max of 362°C for liquid-phase esterified samples and a substantial 24.9% residual weight for gas-phase esterified samples.

Keywords

• nanocellulose
• fatty acid chlorides
• hydrophobicity
• tensile properties
• crystallinity