AbstractThe thermal oxidation of natural rubbers fromHevea brasiliensis(pale crepe and smoked sheet) andParthenium argentatum(Guayule) were studied with differential scanning calorimetry (DSC) using the dynamic method. The atmosphere was oxygen at 110 ml/min and the temperature range was 393° −473°K. The decomposition reactions showed a pronounced exothermic emission with shoulders on the high‐temperature side. The kinetic parameters were computed by using three different mathematical approaches: the heat evolution treatment of Borchardt and Daniels, the diffusion‐controlled method by Jander, and the heating rate method developed by Kissinger and Ozawa. The best agreement between these methods was achieved assuming first order in the Borchardt and Daniels method and three‐dimensional diffusion with the Jander model. The mass influence was analyzed observing that good agreement is obtained working with sample weight in the order of 3–4 mg. Under such conditions the activation energies (Ea) were 16–17, 18–19, and 23–24 kcal/mole for the Borchardt‐Daniels, Kissinger‐Ozawa, and Jander
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