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REACTIONS <br /> POLYOL + TDI ---> URETHANE <br /> WATER + TDI IP co, + UREA <br /> fGAS) <br /> C <br /> FIGURE 2 <br /> t, <br /> One, the polyol reacts with TDI to form polyether urethane rubber <br /> or polymer. <br /> Two, TDI reacts with water to produce urea groups and carbon <br /> dioxide gas. <br /> Both of these reactions produce great quantities of heat which <br /> allows urethane foam to be essentially self curing. <br /> These two reactions take place together. The polymer as it is <br /> formed traps the gas being released. The resulting expansion of the <br /> polymer creates the foam. <br /> Three of the four minor ingredients control the rate of these two <br /> reactions and help to stabilize and produce a uniform cell foam. i <br /> The fourth minor ingredient, the gas producing fluorocarbon, has <br /> a boiling point of 75 degrees F. The heat from the chemical re- <br /> action causes this material to vaporize to contribute additional gas <br /> for expansion. <br /> The two reactions join together the starting molecules to form <br /> giant chains or polymers. The chains are chemically joined to each <br /> other by two types of chemical linkages, urethane and ureas. The <br /> product of the polyol—TDI reaction is a long chain flexible polymer <br /> linked together by urethane groups. <br /> 9 <br /> y <br />