Mechanical performance of polyhydroxyalkanoate (PHA)-based biocomposites

Polyhydroxyalkanoates (PHAs) are biopolyesters synthesized as carbon and energy sources by a wide variety of microorganisms. Among PHAs, polyhydroxybutyrate (PHB) and poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) are frequently considered as biodegradable matrix for natural fiber-reinforced biocomposites. With mechanical and physical properties close to polypropylene, PHB and PHBV, however, are susceptible to thermal degradation and possess a highly brittle structure. These drawbacks prevent them from being used in a broad spectrum of applications. To the contrary, owing to their fully biodegradable nature and high mechanical properties, both PHB and PHBV have high demands in the markets of packaging materials, disposable items, automotive parts, and medical devices.Developing biodegradable composites from PHB and PHBV with enhanced mechanical and acceptable thermal properties is a challenging task for researchers and engineers in meeting the ever-increasing demand for environmentally friendly and sustainable materials. This chapter will review recent developments in the field of mechanical performance of PHA biocomposites. Specifically, the chapter will focus on PHBV blends, natural fiber-reinforced PHBV composites, and PHBV nanocomposites. The overall characteristics of the reinforcing fibers used in PHA biocomposites, including their sources, types, structures, compositions, as well as mechanical properties, will be reviewed. The development of nanotechnology has facilitated new insights into PHA structures, reinforcement mechanisms, and processing options. A variety of potential applications and research trends are anticipated. In this chapter, such new trends in the selection of natural fibers from waste streams rather than from feed crops are introduced.