Etude de la dégradation thermique de deux copolymères réalisés entre l'acrylonitrile ou le méthacrylonitrile et l'α-acétoxyacrylate de méthyle. Analyse thermogravimétrique et chromatographique en phase gazeuse couplée à la spectrométrie de masse

The thermal degradation behaviour of two copolymers poly (acrylonitrile-co-methyl α-acetoxyacrylate) and poly (methacrylonitrile-co-methyl α-acetoxyacrylate) was studied by means of dynamic and isothermal thermogravimetry in the range 246-302 °C and gas chromatography/mass spectrometry analysis. The main volatil products are acetic acid and methyl acetate and methanol in minor amounts. There is no monomer from the first copolymer. The global reaction order is zero over a wide range of conversion (α = 0,1-0,6), then it is one for a > 0,7, with activation energies of 160,5 and 142,9 kJ. mol -1 , respectively. Some amount of comonomers was found in addition in the case of the second copolymer. The kinetic law may be written as: dα/dt = k(C+α)(A - α) where A and C are constants for every temperature. The global activation energy was found to be 127,0 kJ. mol -1 . A kinetic model of a one order reaction with a partial autocatalytic character allows a very good fit of the experimental data with the theoretical curves over a wide range of conversion (α = 0,1-0,8).