Cellulosic Insulation Material I. Overall Degradation Kinetics and Reaction Heats

Abstract

Kinetic studies on the thermal and oxidative decomposition of untreated cellulosic insulation have been carried out with thermal analytical techniques (TGA and DSC) to provide input parameters for smoldering studies of this material. In dry nitrogen, the weight loss proceeds in one overall step that follows a diffusion-controlled rate law with parameters: A = 1.1 × 10¹³ min^-1 and E = 39 kcal/mol. In air the decomposition proceeds in two overall steps, the first of which consumes ca 65 percent of the starting material via a diffusion-controlled rate law and has the activation parameters A = 7 × 10¹⁴ min^-1, E = 41.5 kcal/mol. TGA experiments have shown the first oxidative step to be 0.43 order in oxygen mass fraction in the range of Y_ox = 0.0147 to 0.21. The second oxidation step follows a 3-D diffusion-controlled rate law and has the activation parameters A = 4 × 10¹⁰ min^-1 and E = 39 kcal/mol. Heats of thermal and oxidative decomposition have been determined with the differential scanning calorimeter. Heat release rate is not always in direct proportion lo weight loss rate and a differing rate law is more suitable to describe these data.