Hydrophobization and anti-condensation of cellulose-based films by silanization

The substitution of plastic with eco-friendly alternatives such as cellulose is particularly challenging. One of the primary challenges hindering the application of cellulose films as a substitute for plastics is their inherent hydrophilicity. In this study, we present methods to enhance the water resistance properties of carboxymethylated cellulose fiber (CMF) films through silanization with methyltrichlorosilane (achieved within 5 s) to yield SCMF1, and with tetraethylorthosilicate (completed over 24 h) to produce SCMF2. The silanization was confirmed by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and nuclear magnetic resonance. Various physical and mechanical properties are also assessed. Compared to CMF film (∼55°), the water contact angle increased to 131° and 73.5° for SCMF1 and SCMF2, respectively, indicating a marked improvement in hydrophobicity, especially of SCMF1. Moreover, the porosity of films increased after silanization, rendering them well-suited for various anticondensation packaging applications. This work introduces a novel approach to endow cellulose-based films with hydrophobic and anti-condensation properties for food packaging applications. We found that French fried potatoes, when covered with SCMF2 and SCMF1, maintained their crispness and freshness for longer than those covered by polyethylene. Acute toxicological assessment (24-48 h of exposure) showed that homogenized cellulose films induced a slight decrease in Daphnia magna survival after 48 h, with an estimated EC₅₀ of approximately 2 g/L across all three films. Minimal alterations in swimming behavior were observed at both 24 and 48 h. Overall, the observed toxicity was low compared to other reported cellulose-based materials, supporting the use of cellulose films in food packaging applications. Beyond applications in specific food packaging grades, the innovative post-treatment of cellulose-based film indicates potential to be used in various non-food packaging applications.