Biodegradable and Transparent Water and Oxygen Barrier Multilayer Film

Abstract

Plastic waste remains a critical environmental challenge, with 14.5 million tons generated in 2018 alone, 85% of which ended up in landfills in the US. A key contributor to this issue is the nonrecyclability of multilayer laminations; when different materials are fused, they cannot be easily separated for recycling, thereby exacerbating municipal solid waste problems. This study explores an innovative approach by laminating base layers of poly­(3-hydroxybutyrate-co-3-hydroxyvalerate) or stereocomplex-polylactic acid with a biodegradable coating of poly­(vinyl alcohol) and nanoclay to polylactic acid. Since all the materials are biodegradable, the final structure is also anticipated to be biodegradable in compost environments, opening an additional regenerative end-of-life scenario. The effectiveness of these biodegradable layers was assessed by measuring the moisture vapor transmission rate (MVTR) and oxygen transmission rates (OTR), which ranged from 20 to 30 g/(m2·d) and 54 to 69 cc/(m2·d), respectively. Through optimizing, theoretical rates were estimated at an MVTR of 10 g/(m2·d) at 38° and 90% RH and an OTR of 60 cc/(m2·d) at 23 °C and 50% RH, showcasing low permeability for several biodegradable products. Additionally, water barrier activation energy was measured across four selected structures, ranging from 41 to 58 kJ/mol, indicating that the developed material can potentially package several types of food products in a biodegradable formata significant advancement from previous compostable plastic structures and packaging industry capabilities.