Advancements in the production methods and recycling of multilayer plastics with sustainable applications: A comprehensive review

In recent years, multilayer polymers (MLPs) have become increasingly popular because of their excellent barrier properties and long-lasting durability, which make them well-suited for a wide range of packaging applications. These barrier properties include the prevention of gas (oxygen, carbon dioxide, and nitrogen), moisture, aroma, and light permeation, ensuring product quality, freshness, and extended shelf life. However, their complex structures and widespread use present significant challenges for recycling, with limited practical solutions available. Mono-material MLPs offer a more sustainable and recyclable alternative compared to multi-material MLPs. Additionally, the simplicity and cost-effectiveness of layer-by-layer assembly may provide an advantage over traditional MLP manufacturing techniques. This review focuses on the production, properties, and recycling processes of multilayer films. It covers prior research on various recycling methods, including biochemical, thermochemical, mechanical, and chemical approaches. Specific chemical recycling methods, including methanolysis, aminolysis, delamination, glycolysis, hydrolysis, solvent-based techniques, and catalytic depolymerization, are extensively explored. The review also emphasizes the established pyrolysis method and investigates the potential of biological recycling methods, such as enzyme-mediated catalysis. Emerging technologies and innovative solutions, such as the use of compostable plastics, biodegradable materials, cellulose-based products, and bio-based polymers, are discussed as pathways to achieving a circular economy. The life cycle assessment (LCA) of MLP recycling is analyzed, along with its economic implications. The review emphasizes the importance of ongoing research, innovation, and industry-wide collaboration in addressing the environmental challenges posed by multilayer plastics and fostering a sustainable future. This resource aims to guide prospective researchers in developing and implementing sustainable MLP recycling strategies.