Fire Safety Science Digital Archive

Thermal degradation and thermal oxidative degradation characteristics of Plexiglas G and Lucite were determined using thermogravimetry. The results show that degradation rate of Plexiglas G is sensitive to gas phase oxygen but that of Lucite is much less so. Comparison of derivative thermogravimetry curves between the two samples indicates that at low temperatures Plexiglas G is more stable with respect to degradation in nitrogen. Lucite is initially more stable with respect to degradation in air than is Plexiglas G. A similar trend was observed in a nonflaming gasification study using external radiative heating. It appears that the chemical nature of the degradation processes of the two samples is the same for slow heating thermogravimetry and for more rapid heating (gasification study) simulating a fire environment. In piloted radiative ignition a t 1.8 ~/cm², the ignition delay time of Plexiglas G is about 15% less than that of Lucite. Increasing the radiant flux reduces the difference in ignition delay time between the two samples. The downward flame spread velocity of Lucite is about 20% faster than that of Plexiglas G, but the difference in burning rate between the two samples is very small.