Linear pyrolysis of polymethylmethacrylate during combustion.

Abstract

Polymethylmethacrylate (PMM) surface linear pyrolysis produced by intense surface heating has been studied experimentally. Surface heating was produced by means of a nearby flame established between emerging pyrolysis-product vapors and an impinging jet of oxygen and nitrogen. Surface regression rates between 0.08 and 0.32 mm/sec were achieved by varying the oxygen impingement rate. Very small thermocouples (15/x) embedded in the specimens yielded subsurface distributions. Interpretation of these indicated that: 1) a thin liquidlike transition region existed on the PMM surface; 2) the correlation of regression rate with at the interface between the solidlike and liquidlike regions is generally consistent with regression rate-surface temperature data from hot-plate pyrolysis data of others; 3) the correlation of regression rate with at the interface between the liquidlike region and vapor phase was less consistent with that of others, but was consistent with a correlation of regression rate with our optically measured surface temperature. The implications of these findings are discussed, particularly with regard to analysis of linear pyrolysis data obtained by other techniques. It is concluded that the linear pyrolysis of PMM is sufficiently complex to preclude unambiguous, detailed interpretation on the basis of currently available information.