Surface Modification of Kombucha Bacterial Cellulose for High Water and Water Vapor Barrier: Enhanced Properties through Enzyme Etching and Cardanol-Silane Coating

Abstract

This study presents surface modification for fabricating high water and water vapor barrier, mechanically/thermally strong, nontoxic, and biodegradable Kombucha bacterial cellulose (KBC) films, which have the potential to replace petroleum-based single-use plastic toiletries in hotel industry. The desire for more sustainable, biodegradable, and easy-to-process materials has driven the increasing attention to the application of KBC. However, the hydrophilicity, low reactivity, and prolonged activation have limited the use of KBC. Herein, enzyme etching is shown prior to chemical treatment and can enhance surface area and functional properties of etched KBC (EKBC) films. Improving surface area for condensation reaction between surface hydroxyl group and silane-modified cardanol solution, a hydrophobic byproduct from the cashew nut industry, the surface of KBC can turn hydrophobic with water contact angle up to 108.3° ± 0.4°. The proof of synthesis, grafting, water barrier, mechanical strength, biodegradablility, and nontoxicity is thoroughly investigated. The result shows that etching for 20 min and coated with 2% cardanol-based silane (CBS) achieves the highest water barrier with high biodegradability that can completely degrade within 5 months. As such, coated CBS with EKBC (CBS-EKBC) is shown to possess high sustainability with a simple modification step.