Study On The Pyrolysis Of Phenolic Resin

Phenolic resin has been widely used as a kind of heat protection material at high temperature because of it's excellences in heat-resistance. The pyrolysis research of phenolic resin is considered to have very important significance.The pyrolysis behavior of phenolic resin was studied in a shock tube at high temperatures between 1200 and 1800K. One of the virtues of shock tube experiment is that it can provide a rapid heating rate. The time for heating from room temperature to anticipated temperature is at microsecond magnitude, which could allow the material rise to expected high temperature immediately after heating and avoid the pyrolysis reactions taking place step by step with the increase of temperature. The major gas products were identified as methane, ethene, acetylene, benzene and toluene. The variation of the major products'distribution with pydrolysis temperature was obtained. It was found that the thermal decomposition mechanism of phenolic resin changed a lot within the experiment temperature range. The decomposition mainly took place at the methylene bridges at the temperatures below 1400K, while the cracking of aromatic framework became the major pyrolysis pathway at the temperatures above 1400K, which gave birth to large amount of acetylene.The pyrolysis kinetics of phenolic resin was studied using a shock tube at the temperature range mentioned above. The effect of diffusion on the pyrolysis process was investigated through solving the reaction-diffusion equation. It was found that in this experiment the reaction-diffusion process got steady rapidly, so the effect of diffusion was negligible. The rate constant was determined to be k = 1.85×10⁵exp(-100810/ RT) s^-1 , which was just the intrinsic one of phenolic resin. This result can be used in the calculation of ablation flow field under immediate high temperature conditions, such as the re-entry process.A new method used for thermal analysis kinetics called peak analysis method was developed in this text. This method needs only a few eigenvalues of the experimental curves for the determination of the kinetic parameters. The decomposition kinetic of phenolic resin at low heating rate was studied by thermogravimetry. A peak separation was performed to separate the thermal decomposition into three stages according to the characteristic of the experimental DTG curves. Kinetic parameters of each stage had been calculated using peak analysis method. And a decomposition kinetic model, which was shown to accurately describe the decomposition process of phenolic resin, was obtained by the combination of these three stages.