Saturday, January 17, 2015


1.      Reinforced plastics
The term refers to the polymer products reinforced with fibrous reinforcements in the form of discrete fibers, fiber strands or woven or non woven fabrics.

2.      FRP or GRP: Fiber glass reinforced plastics
Earlier the term referred almost exclusively to the parts made with polyester resins and glass fibers. Now thermoplastic resins are also included as they are also reinforced with glass fibers and molded by injection molding in the same manner as other non reinforced thermoplastics. Hence these materials are also described as FRP.

3.      Low pressure reinforced plastics
It is the term used for parts made with polyester resins. Because they can be cured at no or very low pressures (0-50 psi since volatiles are not given off). Exotic fibers mainly used with epoxy resins include Boron, Graphite, Silicon carbide and improved glass fibers.


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.