Processing and Characterization of Food-Grade Plasticizer-Compatibilized Cellulose Nanocrystals and Ethylene Vinyl Alcohol Copolymer Nanocomposites

In the food-packaging industry, ethylene vinyl alcohol (EVOH) is an attractive material due to its excellent gas barrier properties. Unfortunately, moisture sensitivity drastically limits the use of EVOH for packaging applications. To address this shortcoming, EVOH is often layered with other thermoplastic polymers or blended with nanomaterials to create films suitable for food packaging. However, these current nanocomposite strategies are still quite limited as a large volume of solvent is typically required. In this work, we present an approach to develop a food grade, EVOH nanocomposite material containing cellulose nanocrystals (CNCs) via melt compounding. Two food-grade plasticizers (monolaurin and glyceryl monostearate) were investigated as potential compatibilizers, and the compatibility of both plasticizers with CNCs and EVOH were evaluated using Hansen solubility parameters (HSPs). The Hansen solubility spheres indicated that monolaurin is a good compatibilizer, and it was thus investigated experimentally. Excellent dispersion of CNCs into EVOH was achieved by compounding premixed monolaurin and CNCs, prepared by codissolution/evaporation in a suitable ethanol/water cosolvent. Nanocomposite films with effective CNC dispersion prepared in this study also showed enhanced mechanical, thermal, and water barrier properties. Our results demonstrate the applicability of CNC/monolaurin/EVOH films for packaging applications and demonstrate, for the first time, effective dispersion of CNCs into a food-grade EVOH barrier material using melt compounding.