Blending strategies for green packaging: Enhancing polyhydroxybutyrate performance for sustainable solutions

The rising demand for sustainable alternatives to conventional plastics highlights polyhydroxyalkanoates (PHAs), particularly polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), as promising biodegradable thermoplastics. While PHAs offer advantages like non-toxicity and a reduced carbon footprint, their brittleness, narrow processing window, and high production costs limit their broader use, particularly in packaging, the largest source of municipal solid waste. This review provides an overview of PHAs, emphasizing the properties that make them suitable for packaging and the key factors influencing their market longevity. Blending PHAs with natural polymers, such as polylactic acid, cellulose derivatives, and chitin/chitosan improves mechanical, thermal, and barrier properties while enhancing biodegradability by reducing crystallinity or increasing hydrophilicity, thereby facilitating microbial degradation. Additives such as plasticizers, nucleating agents, and compatibilizers, alongside optimized processing conditions and advanced techniques, like reactive blending and the use of block and graft copolymers, improve interfacial adhesion and blend homogeneity, mitigating brittleness and enhancing flexibility and strength. The thermal instability of PHB, which poses challenges during melt processing, can be addressed by incorporating bioplasticizers to lower its glass transition temperature and melt viscosity, allowing processing at lower temperatures and minimizing thermal degradation. Furthermore, in-situ polymerization and bio-based coupling agents further enhance blend uniformity and overall performance. Special attention is given to the potential of PHB/chitosan blends for developing antibacterial, eco-friendly packaging solutions. By reviewing market trends and advances in PHA processing, this review underscores the potential of PHA-based blends to reduce plastic waste and facilitate their commercialization as sustainable, green packaging materials.