Unitl about myself

Polyurethanes 
Formed by the reaction between diisocyanates and polyols (multihydroxy compounds), polyurethanes are 
among the most versatile of plastics, ranging from rigid to elastic forms. Their major use is for foams, with properties 
varying from good flexibility to high rigidity. Thermoplastic polyurethanes that can be extruded as sheet and film of 
extreme toughness can also be made. 
Polyesters of unsaturated acids 
Certain esters can be polymerized to resin and are used on a very large scale in glass-fibre-reinforced plastics. 

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Unsaturated acid (usually maleic acid in the form of its anhydride) is first polymerized to a relatively short 
polymer chain by condensation with a dihydric alcohol such as propylene glycol, the chain length being determined by 
the relative quantities of the two ingredients The resulting condensation polymer is then diluted with a monomer such 
as styrene and an initiator for addition polymerization added. This mixture is quite stable at room temperature over a 
long period. Frequently, a silicone compound is added to promote adhesion to glass fibres, and wax to protect the 
surface from oxygen inhibition of polymerization. Glass-fibre materials are impregnated with the syrup and 
polymerization is brought about by raising the temperature. Alternatively, the polymerization can be carried out at room 
temperature by addition of a polymerization accelerator to the syrup immediately before impregnation. After an 
induction period, which can be controlled, polymerization takes place, with rapid increase in temperature, to give a 
glass-fibre-reinforced cross-linked polymer, which is effectively a thermoset type of plastic and very resistant to heat. 
The properties of the resin are frequently varied by replacing part of the unsaturated maleic anhydride by anhydrides 
of saturated acids. 
Silicones 
Silicon, unlike carbon, does not form double bonds or long silicon chains. It does, however, form long chains 
with oxygen such as in siloxanes with hydrocarbon groups attached to the silicon; these result in a wide range of oils, 
greases, and rubbers. 
Produced through a series of reactions involving replacement of certain atoms in the chain, silicon resins, or 
silicones, can be used for high- and low-pressure lamination, with glass-fibre reinforcement and with mineral or short 
glass-fibre fillers, or for molding powders. The outstanding characteristic of these products is high dielectric strength 
(that is, they are good insulators at high voltages) with low dissipation over a wide temperature and humidity range. 
Silicones are not distorted by heat up to 400 С. They are also physiologically inert and therefore valuable for 
prostheses (artificial body parts). 

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