The Relation Between the Heat of Combustion and the Oxygen Index for High-Polymeric Materials

Abstract

Values of heats of combustion and oxygen indexes cited in the literature were used to develop the following equations: Oxygen Index = 0.0126 (mean heat energy of limiting heat flux, kcal/mole) - 0.036, and Oxygen Index = 0.01286 (mean heat energy of limiting heat flux, kcal/mole) - 0.044. The first equation applies both to high polymers and light fuels, whereas the second equation applies to high polymers only. Experimental heats of combustion and oxygen indexes were determined for some chemical isomers (homopolymers) and copolymers of ethylene-vinylacetate and ethylene propylene; these verified the utility of these equations. It was also determined that the heat required to raise the oxygen index by 1% is from -100 to approximately -44 cal/OI for easily-flammable materials, -23 to approximately -14 cal/OI for slow-burning polymers, and +6 cal/OI for the self-extinguishing polymer. Copolymers have oxygen index values both above and below the average of the OI values for their components.