Temperature inside burning polymer specimens: Pyrolysis zone and shielding

Abstract

Abstract On the basis of two examples, temperature measurements are proposed within burning polymer specimen during the cone calorimeter test; especially to gain deeper insight into the actual pyrolysis conditions and flame retardancy mechanism. The heating and pyrolysis within a poly(methyl methacrylate) specimen were characterized, discussing the characteristic maximum heating rates (165−90°Cmin −1 decreasing with depth within the specimen and >275°Cmin −1 at the initial surface), pyrolysis temperature (454−432°C decreasing in accordance with decreasing heating rates), thickness of the pyrolysis zone (0.5–1.3 mm) and its velocity (1.2−2.1 mm min −1 ) as a function of sample depth and burning time. Thermally thick behaviour corresponds to a pyrolysis zone thickness of 0.74 mm and a velocity of 1.51 mm min −1 and occurs until the remaining specimen thickness is less than 8 mm. The shielding effect against radiation occurring in a layered silicate epoxy resin nanocomposite was investigated. It is the main flame retardancy effect of the silicate‐carbon surface layer formed under fire. The reradiation from the hot surface is increased by a factor of around 4–5 when an irradiance of 70kWm −2 is applied. The energy impact into the pyrolysis zone is crucially reduced, resulting in a reduction of fuel production and thus heat release rate. Copyright © 2009 John Wiley & Sons, Ltd.