Compostable plastic/paper composites with high gas/moisture barriers for sustainable beverage bottles

Currently, the world is facing a major plastic waste problem. Poly(ethylene terephthalate) and polyolefins are primary base materials in the beverage packaging industry, constituting a significant portion of plastic waste. These materials are often processed as multilayered films to meet high-barrier requirements, rendering their recycling difficult. Furthermore, these petroleum-based plastics persist in landfills without undergoing degradation. Accordingly, herein, we developed compostable plastic/paper composite-based bottles that can replace non-degradable plastic bottles. Crystalline structure of bio-based paper was rearranged by mercerization that modifies the cellulose surface to enhance its pervasive ability with poly(butylene succinate-co-butylene adipate) (PBSA). Introduction and combination of the oligomer and polymer states of PBSA facilitated strong paper-polymer interactions and resulted in superior gas/moisture barrier properties. Unlike the cases of conventional paper-based containers, which are prone to deformation under external forces, the flexible yet robust coating layer of this composite provides resistance to deformation, minimizing deterioration of properties under repeated bending forces. Moreover, all ingredients used in this composite are fully bio-based, and the composite demonstrates approximately 70 % decomposition during an 18-week composting test. Given its significant potential to contribute to the realization of a plastic-free lifestyle in the near future, conducting comprehensive evaluations on biodegradability and toxicity in real environments remains as the crucial step towards the successful commercialization.