Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lan Gao Use available evidence to gather and present data from secondary sources and analyse the properties in the recent developments and use of a named biopolymer. This analysis should name a specific enzyme or organism used to synthesise the material and an evaluation of the use of potential uses of the polymer used based on their properties. Poly (hydroxyalkanoates) or PHAs are a group of biopolymers produced from glucose using a bacterial catalyst. The property of the polymer produced depends on the bacterial strain and the conditions under which the fermentation process takes place. The polymers can be either thermoplastics or elastomeric plastics. These polymers are originally used by the bacteria for energy storage but have been found to have potential to replace the oil based thermoplastics. PHA’s are more desirable than thermal plastics as they are renewable resources and do not have the same disposable problems as thermo plastics due to their ability to biodegrade. The first PHA to reach the market was Polyhydroxybutyrate or PHD. It is synthesised by using the microbes Alcaligenes eutrophus or Bacillus megaterium. The bacteria are fed on glucose and can create polymers of up to 80% of their dried weight. These bacteria have undergone genetic modification in order to increase the yield of polymer. This has resulted in the price of production falling from $800 a pound in 1980’s to <$1a pound today. The glucose used is usually wastes from places such as sugar mills and milk processing. By controlling the carbon sources of the bacteria changes the properties of the given polymer. Originally the first PHB produced was too brittle to be of much use. However it was discovered that when propionic acid was added to the bacteria’s diet a new polymer was produced which was far more flexible. Polyhydroxybutyrate-hydroxyvalerate or P (HB-HV) is formed with the use of Alcaligenes eutrophus and is fed precise proportions of glucose and propionic acid. By making the polymer more flexible it has expanded the available uses of this polymer. PHA’s are marketed under the name Biopol. These polymers have an elasticity of 5% to >10000% elongation at break, UV stability, water stable yet biodegradable in marine, soil, compost and waste treatment environments, excellent film forming properties from aqueous latex and environmentally compatible. PHA’s can be used as polymer performance enhancers, non-woven fabrics, film and fibre, adhesives and coatings, binders for metals, biodegradable packaging and water resistant coatings. They are increasingly popular due to two major characteristics that they posses. PHA’s are both biocompatible and biodegradable. Due to this biocompatibility they can be used in medical application such as capsules for controlled drug release, surgical sutures, bone plates and wound are without the fear of a reaction from the patient or the polymer being toxic. They have the potential to be used a structural materials in personal hygiene products and packaging applications. Although the cost of PHBV has fallen it is still far more expensive than normal petroleum based polymers. The fact that PHA’s are biodegradable makes them perfect for disposable packaging. It is currently used in cosmetic containers and commercial films and paper coatings. There is also researching to creating a biodegradable fishing net which will lead to decreased instances where sea creatures are caught in disposed nets.