Biodegradable and Transparent Water and Oxygen Barrier Multilayer Film

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.