The heats of combustion of polytetrafluoroethylene (teflon) and graphite in elemental fluorine

Abstract

Bomb calorimetric measurements are reported for the combustion in fluorine of polytetrafluoroethylene (Teflon) and graphite-polytetrafluoroethylene mixtures. Mass spectrometric examination of the product gases showed CF4 to be the only major product with C2F6(g) present in only very small amounts. The completeness of combustion of the graphite was determined by chemical analysis of combustion residues and found to range from 97 to better than 99 percent. From the combustion data, the heats of formation ?H?f298[CF4(g)] and ?H?f298[C2F4 (solid polymer)] were determined to be -222.87 ? 0.38 kcal mol-1 and -197.82 ? 0.39 kcal (gfw C2F4)-1, respectively. The uncertainties are estimates of the overall experimental errors. A previously reported value for the heat of formation of AlF3(c) is adjusted to be consistent with the present work. An evaluation of other data on CF4 is presented. The heat of formation of CF4(g) is combined with other work to derive the heats of formation of HF solutions at three specific concentrations.