Thermogravimetric studies of polymethylenes and polyethylenes

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Abstract
Seven samples of polymethylene prepared during polymerization of diazomethane having different initial molecular weights and five samples of polyethylene (Lupolen type) having a different number of branches were studied by thermogravimetric analysis using Freeman Carrol's and Fuoss's methods to determine the number of CH3 groups per 1000 carbon atoms. The calculated activation energies reflect the effect of both molecular weight and the number of branches on the thermal stability of the polymer. Activation energy values decrease with the lowering of the molecular weight Mv of the polymethylene sample. This decrease of Mv occurred during the initial etching of the sample in fumic nitric acid. The activation energies of the branched polyethylenes decrease with the increase of the number of branches. Thermal stability of branched polyethylenes is lower than that of linear polyethylene.

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