| An assessment of the experimental uncertainty in obtaining the kinetic activation energy from Thermogravimetric data is presented. A neat phenolic resin, Borden SC1008, was heated at three heating rates to obtain weight loss versus temperature data. Activation energy was calculated by two methods: the traditional Flynn and Wall method based on the slope of log q versus 1/T, and a modification of this method where the ordinate and abscissa are reversed in the linear regression. The modified method produces a more accurate curve fit of the data. An uncertainty analysis using the modified method yielded a 60% uncertainty in the average activation energy. Based on this result, the activation energy for a carbon-phenolic material was doubled and used to calculate the ablation rate in a typical solid rocket environment. Doubling the activation energy increased surface regression by 3%. Present techniques that use the traditional Flynn and Wall approach should be changed to the modified method. |
