The thermal decomposition of polyalkyl methacrylate such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate and methyl methacrylate-ethyl methacrylate copolymer was studied using a thermogravimetry with nitrogen gas feed rate of 50 ml/min at various heating rates from 1 to 20 ℃/min, and various heating temperatures from 200 to 370 ℃. Viscometry techniques were also used to measure molecular weight changes during the thermal decomposition.
The mathematical methods, Kissinger, Chatterjee-Conrad, Friedman, Second derivative, Horowitz-Metzger, Ozawa and lsothermal method were used to obtain values of activation energy of decomposion reaction.
The activation energies evaluated by the above methods except Chatterjee-Conrad method agree with each other very well.
The values of activation energy evaluated by viscometry are also similar with those by thermogravimetry.
The thermal degradation of polyalkyl methacrylate was considered to be carried out by main chain scission, and the values of activation energy decreased in the order of methyl, ethyl and buthyl group.
The thermogravimetric trace curve agreed with the theoretical equation.
The value of activation energy of the copolymer obeyed the addition rule.