KINETICS OF PYROLYSIS MASS-LOSS FROM CURED PHENOLIC RESIN

Knowledge of the kinetics of phenolic resin pyrolysis is critical to t he accurate modeling of ablatives used in rocket nozzle and re-entry e nvironments. Most employ thermogravimetry to study this phenomena. Nea rly all of the previous studies on ablative materials have utilized fa irly slow heating with respect to the use environment, This has forced analysts to extrapolate to the much higher rates occurring in the use environment. The high heating rate predictions of these models sugges t that pyrolysis can be postponed to much higher temperatures. This ha s had dramatic effects on the predicted mechanical response of the mat erial under night conditions. To avoid these large extrapolations, lab oratory data was required at or near the high heating rates seen in th e use environment. A new facility was constructed that is capable of o btaining data at substantially higher heating rates than are currently available. Cured SC 1008 phenolic resin in powdered form was heated a t eight heating rates ranging from 0.25 to 2500 degrees C/min, The dat a indicates that the weight loss behavior of this material at very hig h heating rates exhibits a much reduced kinetic response over what was previously predicted, and that this may be due to a change in chemica l reaction mechanism.