Saturday, January 17, 2015


Various modifying agents are used with polymers to obtain certain specific properties. These modifiers are known to be microbial nutrients. This includes some lubricants and plasticizers. With the large number of destructive agents and the adaptability of each, it is highly probable that there are no plasticizers that are completely free from fungal or bacterial attack. Some are readily used by the microorganism as the source of carbon. As the microorganisms grow, they secrete digestive enzymes which accelerate the degradation process of the film by advancing the mycelial growth. The destruction of polymer by plasticizer results in tack and exudation, embrittlement, weight loss and discoloration.
Polyolefins in their unmodified form exhibit excellent resistance to biological destruction. When these polymers are compounded with additives or plasticizers the biological decomposition varies in degree and also is of various types. Plasticizers are substances that are added to plastic compounds to improve their flexibility, extensibility and processibility. Deterioration of the polymer by microorganisms is chemical, involving changes in composition and breaking of chemical bonds. It is the result of enzymes produced by the microorganisms. Various plasticizers that exhibit higher susceptibility towards microbial attack are: acetals, butyrates, laurates, oleates, sebacates, epoxidized oil, epoxidized tallate esters, polyester, glycolates, stearates, abiotic acid derivatives, aliphatic acid derivatives, aliphatic alcohols, n-phthalic acid derivatives, rcinoleates, succinic acid derivatives. Vegetable oils like tung oil, linseed oil, soy bean oil, cottonseed oil, castor oil, dehydrated castor oil, ground nut oil, etc, also exhibit higher susceptibility towards microbial attack.

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