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High-temperature degradation of reinforced phenolic insulator

1998    Pektas, I

The thermal degradation of graphite and glass-reinforced phenolic insulators have been studied at high temperature by using thermogravimetric (TGA) and differential scanning calorimetric analyses. TGA analysis was carried out in a stream of pure nitrogen over temperature range ambient to 900 degrees C and DSC analysis to 500 degrees C. A heating rate of 10 degrees C/min was used for the determination of degradation temperature and heating rates of 5, 10, 20, 30, and 50 degrees C/min were used for the estimation of degradation temperature (T-max) of the insulator at high-temperature service and calculation of activation. Activation energy of phenolic resin was calculated as 356 kJ mol(-1) using the Ozawa method. T-max was determined as 661 degrees C for 20% conversion. The specific heat capacity of graphite phenolic was found as 970 J kg(-1) K-1 at 100 degrees C. The half-life of the phenolic resin was determined to be approximately 116.2 s at 3500 degrees C. The thermal analysis has been conducted using transient heat conduction and the in-depth temperature distribution was evaluated along the rocket nozzle. The better insulator thickness, including a safety factor for graphite and E-glass-reinforced phenolics were calculated as 3 and 2 mm, respectively. (C) 1998 John Wiley & Sons, Inc.