Correlation of electrical conductivity and thermal decomposition of phenolic materials

Changes in the temperature dependence of the electrical conductivity associated with thermal decomposition of several phenolic materials have been measured to 6000 C in nitrogen and air environments. The materials were phenolic resins reinforced with chopped glass fabric. Thermal decomposition product data and mass loss data were obtained from mass spectroscopy and thermal gravimetric analysis. Results showed that peaks in the conductivity temperature dependence were associated with material decomposition and/or outgassing, and that the presence of oxygen accelerates decomposition above approx. 4500 C. In the region of ohmic conduction (electric fields less than or equal to 4 x 10 to the 3rd power V/cm), there was excellent correlation between thermal decomposition characteristics and the temperature dependent electrical properties. This correlation suggests that electrical conductivity can be used as a thermal analysis tool in characterizing phenolic materials.