Highly hydrophobic and moisture barrier nanocellulose based films produced via spray deposition

Nanocellulose (NC) films are gaining popularity in recent years owing to their recyclability and biodegradability; however, the commercialization of this material is limited by environmental and moisture barrier constraints. The incorporation of carboxymethyl cellulose (CMC) with NC significantly improved the barrier performance but the resultant films were quite hydrophilic and hence completely disintegrated in water. The aim of this study is to produce hydrophobic NC/CMC films without compromising their barrier characteristics. For this purpose, the optimized content of alkyl ketene dimer (AKD) was spray-deposited on the fully and partially dried NC/CMC films and their hydrophobic, barrier and mechanical properties were assessed. The deposition of AKD has improved the hydrophobicity and flexibility while maintaining the barrier properties of the films. However, their tensile index values decreased by 26–29% as compared with the neat NC/CMC films, but the values remained in acceptable range. Additionally, the partially dried spray deposited AKD-NC/CMC films have shown superior results as they showed higher hydrophobicity (θ = 127° ± 3), while lower percentage of mass loss after immersion for 48 h in water (15%) as compared with the fully dried spray deposited AKD-NC/CMC films. Graphical abstract: [Figure not available: see fulltext.]