Fire Safety Science Digital Archive

In this work the influence of paint loading on the time to ignition is investigated for chipboard and plywood. Unpainted and painted specimens, 100-mm-square, 18-mmthick, were subjected to constant incident heat fluxes of 35, 50 and 65 kWm-2 in a cone calorimeter. The time to ignition, mass loss rate and heat release rate are reported as functions of time and of the initial dried mass of paint on the sample (as opposed to number of coats reported in previous work by others). It was found that addition of a small amount of paint (up to 2 g or 200 g/m² - equivalent to 2 coats) increased the ignition time by a maximum factor of approximately two. However, addition of even more paint (up to about 4.5 g or 450 g/m² - equivalent to 5 coats) actually reduced the ignition time by up to a factor of approximately 7 relative to the unpainted material. A critical paint loading appears to exist (which decreases with increasing external heat flux), at which the physical mechanism controlling the ignition process changes. A mathematical model with simple kinetics was used in order to interpret the results and understand the ignition behaviour.