Properties of PHB

1. PHB is water insoluble and relative ly resistant to hydrolytic degradation. This differentiates PHB from most other currently available biodegradable plastics, which are either water soluble or moisture sensitive.
2. PHB shows good oxygen permeability.
3. PHB has good ultra-violet resistance but has poor resistance to acids and bases.
4. PHB is soluble in chloroform and other chlorinated hydrocarbons.
5. PHB is biocompatible and hence is suitable for medical applications.
6. PHB has melting point 175⁰C., and glass transition temperature 15⁰C.
7. PHB has tensile strength 40 MPa which is close to that of polypropylene.
8. PHB sinks in water while polypropylene floats. But sinking of PHB facilitates its anaerobic biodegradation in sediments.
9. PHB is nontoxic.

Parameter	Polypropylene (pp)	PHB
Melting point Tm [0C]	171-186	171-182
Glass Transition Temperature Tg [0C]	-15	5-10
Crystallinity [%]	65-70	65-80
Density [g cm-3]	0.905 - 0.94	1.23 - 1.25
Molecular weight Mw (x10-5)	2.2 - 7	1 - 8
Molecular weight distribution	5 - 12	2.2 - 3
Flexural modulus [GPa]	1.7	3.5 - 4
Tensile strength [MPa]	39	40
Extension to break [%]	400	6 - 8
UV resistance	poor	good
Solvent resistance	good	poor
Oxygen permeability [cm3m-2atm-1d-1]	1700	45
Biodegradability	-	good
US Annual production M. tonnes	1.8	not determined
Other	due to low density floats in aquatic system	due to more density goes to the sediment in aquatic system.

Bioplastics are making commercial and scientific progress continuously. W. R. Grace was the American company which carried out t he work on PHB as early as 1960s. The work was then curtailed because at that time the techniques available for extraction were not able to provide a product thermally stable in processing. The development of PHB was begun by ICI in 1975-6 as a response t o increase in oil prices. ICI started marketing BIOPOL in 1982. ICI, the UK chemical group, has opened a plant at Billingham in North-east of England to make 300 tonnes of Biopol a year, which it says is the first fully biodegradable commercial plastic. The company plans to raise its annual production of this Nature's plastic to 5000 tonnes very soon. At present, Biopol costs about pounds 10 per kg., 20 times more than conventional plastic. Costs can be reduced to some extent by scaling up of the product ion. Even at its current price, ICI has plenty of buyers for limited amounts of Biopol hat they produce.
Australia's A$1 billion raw sugar industry is going to follow Brazilian researchers into new industry producing plastic from sugarcane. Australia's sugar to plastic plans are based on technology held by Procter & Gamble Co. which uses sugarcane genes to produce a plant which produces the polymer poly(3-hydroxybutyrate) (PHB).
Brazilian sugar industry, through the largest industry co-operative Copersucar, is well advanced in an ambitious non-genetic project to produce PHB by using bacteria to convert sugar to plastic.