Green Polymer Composites Technology

Abstract

Polyhydroxyalkanoates (PHAs) belong to the family of bacteria produced polyesters, which are truly biodegradable, biocompatible, and melt processable. Short chain length PHAs, containing 3–5 carbons in their repeating unit, have similar properties to polypropylene, and medium chain length PHAs, containing 6–14 carbons in their repeating unit, are elastomers. PHAs in their neat forms have found a wide range of applications as general-purpose commodity bioplastics and value-added medical materials for tissue engineering scaffolds and drug delivery carriers. PHAs composites provide another dimension for tuning the properties of PHAs. In this chapter, the properties of PHAs composites and the processing technologies are reviewed according to target application areas, giving an insight into key issues in composite manufacturing. For using as general-purpose commodity bioplastics, the commercially available PHA members, poly (3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) are reinforced using cheap renewable fibres of vegetable origin to offset the production cost and enhance their mechanical properties. For using as biomedical materials, high purity of PHAs (PHB, PHBV, and poly[3-hydroxybutyric- co-3-hydroxyhexanoate] [PHBHHx]) are reinforced using bioceramics such as hydroxyapatites and various bioactive glasses to enhance their bioactivities and mechanical properties. PHAs composites will open a new avenue towards large-scale application of PHAs. On the basis of current limited successes, further improvement in reinforcing effects relies on the development of suitable surface modification technology to provide sufficient interfacial bonding and the exploration of nanoscale fillers.