Multilayer Packaging Films Designed for Deconstruction: Biopolyesters with Water-Soluble Barrier Layers

Growing consumer demand for environmentally friendly packaging materials has renewed interest in processing and design of biodegradable polymers. Herein, multilayer films composed of poly(butylene adipate-co-terephthalate) (PBAT) and poly(vinyl alcohol) (PVOH) were successfully fabricated via coextrusion blown film technology. To achieve high strength and low permeability, PBAT, known for its flexibility, toughness, and biodegradability, was used as the outer layer, whereas PVOH, with exceptional oxygen barrier and water solubility characteristics, was used as the core layer in the multilayer structure. With the inclusion of the PVOH core layer in the multilayer, the tensile strength, elongation at break, and oxygen barrier properties of the PBAT/PVOH film were greatly improved. The cross-sectional morphology and peel test results proved acceptable interlayer adhesion between layers. Oxygen permeation rate (OPR) and water vapor permeation rate (WVPR) testing showed that the multilayer sample provided an OPR of 4.20 cm3·mil/m2·day·atm at 0% relative humidity and a WVPR of 1.40 g·mil/m2·day at 5% relative humidity, suitable for standard packaging requirements. Moreover, aqueous dissolution selectively removes the PVOH layers and separates the PBAT layers from the multilayer films. Hydrolytic and microbial biodegradation studies of the recovered PBAT layers under controlled conditions showed accelerated degradation behavior, undergoing more than 80% polymer mass loss in 7 days. Given that all of the components are soluble and biodegradable, the final polymer films offer sustainable end-of-life options compared to incumbent materials.