Bilayer biocomposites based on coated cellulose paperboard with films of polyhydroxybutyrate/cellulose nanocrystals

In this paper, a biodegradable bilayer nanocomposite based on reinforced polyhydroxybutyrate (PHB) with cellulose nanocrystals (CNC) and cellulose paperboard was prepared. In order to obtain optimal properties two different processing methods were studied: casting and compression molding. Compression molding was selected as the most effective technique to achieve a continuous layer of PHB covering the entire surface of the paperboard. Mechanical and barrier properties of the composites were optimized, using the least amount of PHB due to its high cost compared to fossil-derived polymers. Then, the bilayer nanocomposite was produced according to the selected method and the least PHB proportion, demonstrating that PHB/CNC coating overcomes water sensibility of the cellulose paperboard and exhibited a performance enhancement without detrimental effect of the pristine PHB and paperboard properties. It was demonstrated that PHB and PHB/CNC have the potential to replace non-renewable polymers as fully bio-based materials, obtaining paperboard coatings with environmental advantages, such as non-toxicity, high recyclability and biodegradability.