Polyhydroxybutyrate, a biodegradable polymer, has so far been produced using enzymes. These laboratory routes to make PHB have used enzymes to convert glucose to hydroxybutyrate, which is subsequently polymerized. The resultant is a brittle product and therefore has limited uses. Two scientists, who were recepients of Philip Morris 2006 Research Award, have developed a new catalyst system based on silica, cobalt & nitrogen. The starting material used for polymerization is propylene oxide and carbon monoxide. Professor Bernahrd Rieger of Ulm University and Dr Gerrit Luinstra of BASF in Ludwigshafen first revealed the technique earlier this year, said to be more economical than previous laboratory routes. The development promises PP-like performance with a 50% reduction in oil consumption
The catalyst used may be modified so that PHB with harder or softer characteristics is obtained, enabling the material to be used in applications as varied as film for shopping bags or sheet for yoghurt cups. Injection mouldable product also could be developed for several application segments including automotive. Polyhydroxybutyrate (PHB) and its copolymers with polyhydroxyvalerate (PHV) are melt-processable semi-crystalline thermoplastics made by biological fermentation from renewable carbohydrate feedstock. They have been described as �the first example of a true thermoplastic from biotechnology� and are also biodegradable. Although quite stable under everyday conditions they degrade slowly in the body and when composted or in landfill sites.
Copolymer has better prospects since it has better properties compared to homopolymers. Homopolymer seems to be too brittle. Besides, homopolymer has a tendency to biodegrade much faster and therefore lose value due to limited service life. One weaker aspect of this group of polymer and copolymer is that both of them have poorer chemical resistance. They are easily attacked by acid as well as alkalies. Chlorinated solvents also dissolve this group of polymer and copolymer.
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