Devolatilization wave structures and temperatures for the pyrolysis of polymethylmethacrylate, ammonium perchlorate, and coal at combustion level heat fluxes.
Data are presented for the surface pyrolysis temperatures, ts, and for the devolatilization mass loss rate per unit area, m, for polymethylmethacrylate (pmma) exposed to a laser beam at incident flux levels of 15 to 500 w/cm2. After a brief induction time during which the surface is being heated to ts, the measured m values are thereafter steady state in time, and are linearly related to the net absorbed flux, iabs. The measured values for m are in good agreement with that derived from the first law of thermodynamics. Kinetically, this equation represents a devolatilization wave front whose propagation rate and maximum temperature are both heat- transport controlled, and determined by the magnitude of the driving flux, iabs. The available data for ammonium perchlorate and for coal are also shown to obey a similar relationship, and the same heat-transport-controlled process appears to govern their pyrolysis and devolatilization kinetics.