chapter  13
21 Pages


PHAs are thermoplastic polymers with material properties ranging from brittle to flexible to rubbery, according to the presence of different kinds of hydroxyalkanoic acids. From a general point of view, the most attractive characteristics of these polymers are their material properties which are similar to those of conventional synthetic plastics, their biodegradability, their hydrophobicity and the possibility to use renewable resources for their production. On the other hand, their prices are still much higher than those of petrochemical derived plastics; e.g. US$16/kg for BIOPOL, a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate [P(3HB-co3HV)l manufactured in the UK by Zeneca BioProducts, in comparison with US$l/kg for polypropylene (Lee, 1996), the synthetic polymer possessing material properties similar to those of PHAs.