(644f) Sustainable Hydrophobization of Cellulose-Derived Thin Films for Food Packaging

Cellulose is the most abundant biopolymer on the planet, making it an obvious feedstock for replacing petroleum-based polymeric materials with more sustainable options. Here, we are using a cellulose derivative, carboxymethyl cellulose (CMC) as our primary material, since it allows us to use standard solution casting methods with water as a solvent. The CMC films are cross-linked using ethylene glycol diglycidyl ether (EGDE) and subsequently characterized by in-situ oscillatory shear rheology, Fourier transform infrared spectroscopy (FTIR), and small angle X-ray scattering (SAXS). Literature-based methods were used to determine bulk properties such as water vapor permeability, swelling ratio, tensile strength, and %elongation at break to assess their applicability for food packaging. The unmodified films were found to have decent mechanical properties but a very high-water vapor permeability compared to synthetic films, so an immersion-hydrophobization procedure was developed to increase the films’ hydrophobicity. In this procedure, an esterification reaction occurs between a fatty acid derivative and one of the hydroxyl groups on the cellulose chain. Hydrophobization was carried out using a variety of plant oils and fatty acids (soy bean oil, corn oil, rapeseed oil, and stearic acid), which were chosen due to their ease of use, wide availability, and relatively low cost. The hydrophobization efficacy was measured using water vapor permeability and water contact angle. In addition to the hydrophobicity, additional bulk properties, such as tensile strength, water vapor permeability, and % elongation at break were measured before and after hydrophobization.