Experimental and modelling studies on the kinetics and mechanisms of thermal degradation of polymethyl methacrylate in nitrogen and air

• TGA and DSC were used to assess the decomposition and phase behaviour of PMMA.
• Gas phase was analysed through FTIR.
• Mechanism of the thermal decomposition of PMMA was proposed.
• Kinetic parameters were calculated by employing a Genetic Algorithm.
• Model was validated for different oxygen concentrations (10.5 and 15 vol.%).

Modelling of spread of fires and their extinguishment in solid materials still present a significant challenge. In order to reliably predict the behaviour of a material in a fire scenario, an adequate description of the processes occurring at the gas/solid interface is highly crucial. In this context, those fire scenarios involving polymeric materials are of primary importance because of their increasing use as components in buildings and in transportation. The purpose of this study is to propose an accurate model for the thermal degradation of polymethyl methacrylate (PMMA) by primarily using thermogravimetric analysis (TGA). TGA in non-isothermal conditions, together with Fourier-transform infrared spectroscopy (FT-IR), was applied to investigate the thermal degradation of black PMMA in inert (nitrogen) and oxidizing (air) atmospheres, at different heating rates. The volatile degradation products as well as mass loss history provided sufficient information regarding the kinetics and possible degradation mechanisms of PMMA. A genetic algorithm (GA) was applied to estimate the kinetic parameters, which showed an excellent agreement with corresponding experimental observations for several heating rates and at different atmospheres (0, 10.5, 15 and 21 vol.% O2).