PHB

Polyhydroxybutyrate (PHB) is a polyhydroxyalkanoate (PHA), a polymer belonging to the polyesters class that are of interest as bio-derived and biodegradable plastics. Properties: Water-insoluble and relatively resistant to hydrolytic degradation. This differentiates PHB from most other currently available biodegradable plastics, which are either water-soluble or moisture-sensitive. Good oxygen permeability. Good ultra-violet resistance but poor resistance to acids and bases. Soluble in chloroform and other chlorinated hydrocarbons.[8] Biocompatible and hence is suitable for medical applications. Melting point 175 °C., and glass transition temperature 2 °C. Tensile strength 40 MPa, close to that of polypropylene. Sinks in water (while polypropylene floats), facilitating its anaerobic biodegradation in sediments. Nontoxic. Less 'sticky' when melted