Properties and applications of bacterially derived polyhydroxyalkanoates

The polyhydroxyalkanoates represents a range of polyesters produced from renewable resources by bacterial fermentation. The class includes the 3-hydroxybutyrate-co-3-hydroxyvalerate polymers marketed under the Biopol trademark. [Pg.88]

These copolymers are semi-crystalline with melting temperatures ranging from 120 to 180 °C depending on the copolymer composition. Flexibility and ductility improves with increasing hydroxyvalerate copolymer content. [Pg.88]

The crystallization behaviour of these polymers has been studied extensively. Both monomer units have very similar crystal lattice requirements and exhibit the phenomenon of isodimorphism. Compared with other thermoplastics, the nucleation density is relatively low leading to slow rates of crystallization. This potential problem has been overcome at the commercial scale by the use of nucleant systems. [Pg.88]

The copolymers are truly biodegradable and are enzymically degraded by a wide range of bacteria, fungi, and algae. Degradation times depend on the environment and material form and can range from weeks to over a year. [Pg.88]

As the materials are thermoplastic, they can access injection moulding and extrusion blow moulding technologies. Cast film, sheet and tubes can also be formed. Paper and board coating has also been demonstrated on a commercial scale. [Pg.88]

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