LAUSR

Abstract Polyhydroxyalkanoates (PHAs), comprising a broad range of bio-based polymeric materials, are natural biodegradable polyesters formed by microorganisms. The simplest, best characterized and extensively studied member of the PHAs family is Poly(3-hydroxybutyrate) (PHB). PHB is expected to play a decisive role, as regards the bioplastics sustainability, due to high biodegradability in various natural and controlled environments, biocompatibility, manufacturing processing through direct extraction from bacteria cell without the intermediate stage of polymerization. Several drawbacks, though, still restrain pure PHAs applications, compared to conventional synthetic plastics. Low ductility, excessive manufacturing cost, susceptibility to thermal degradation render PHAs less competitive, than ordinary plastics, as packaging materials or biomaterials. Alternative strategies are needed to improve the PHB polymer behaviour, targeting its main deficiencies of brittleness and sensitivity to thermal degradation. Subsequently, PHAs, including PHB, are properly modified and processed to achieve production of rigid or flexible bio-based plastics with enhanced performance for various applications. Selected PHB modification methods are reviewed and discussed. Processes for upgrading the properties of PHB, through its blending with raw materials of natural origin or other bio-based and biodegradable polymeric materials, are epitomized. Various additives used and their role in the modification of PHB are reviewed. Moreover, the functionalization of PHB, via chemical modification synthetic routes, such as block and graft copolymerization techniques, is presented. The various processing techniques and conditions for the effective PHB films manufacturing, sheets and other articles are reviewed. The integrated review approach introduced offers a better insight on the alternatives’ effectiveness to improve the PHB performance, by overcoming its main drawbacks.