26 November 2010


Biodegradable polymers constitute a loosely defined family of polymers that are designed through the action of microorganisms. The application plurality and versatility of this class of material have gone up in multiple order in replacing wood, paper and conventional metals. Four major biodegradable polymers commercially available are:-

Starch based polymers, poly (lactic acid), polyhydroxy alkanoates, aliphatic/aromatic co-polyesters.
Biopolymers based on starch are mainly Novon polymers and Mater-bi. These can be processed on injection moulding, blowmoulding, thermoforming etc. Lignin, another variety, is an amorphous aromatic network polymer second to cellulose in natural abundance. These can be used to replace about 35-40% of the phenol in phenol formaldehyde resin and a number of applications are there. Based on plants, polyhydroxy alkanoates is of great importance. Polyhydroxy butyrate provide tremendous versatility in terms of end use applications. As a polymer, PHB compares well with polypropylene in molecular mass, melting temperature and tensile strength.

Biodegradable eco-friendly polymers can be obtained from cashew nut shell liquid (CNSL). Addition of CNSL into phenol leads to decrease in tensile strength but an improvement in impact strength and electrical properties of the resol resin. Best example is Anorin 35 and 38. One of the remarkable achievements in converting cardanol into high performance polymers was the successful synthesis of liquid crystalline polymers. Biopolymers from soyabean soy protein produce fully biodegradable thermoplastic composition that can be blown into films. Bioplastics made out of cornstarch-polyester blends are already being commercialized in US and Japan.

By studying the causes of non-biodegradability of plastics, high molecular weight, lesser chain mobility and hydrophobicity are the main factors. Enzyme catalysed biodegradation mechanism is a two-step process carried out by mesophilic and thermophilic bacterial species. One of the advanced applications includes micro/nanospheres of biodegradable polymers for controlled release of anti-cancer drugs. Based on the information that I have found, I would say that biodegradable polymers are a reality. The effect of plastic material could be reduced to an eco-friendly level by initiating awareness programme among the end-users and processors. It is not polymers that totally replace traditional plastic, but they will certainly help relieving environmental and regulatory pressures. All things considered, total or near total use of eco-friendly biodegradable polymers is in reach within the near future.

Alex Daniel & Rajeesh.S.Nair

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