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The thermal oxidation of guayule and hevea rubbers by dynamic differential scanning calorimetry
Author(s) -
PonceVélez M. A.,
CamposLópez E.
Publication year - 1978
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1978.070220908
Subject(s) - differential scanning calorimetry , activation energy , materials science , diffusion , natural rubber , analytical chemistry (journal) , chemistry , composite material , thermodynamics , chromatography , organic chemistry , physics
The thermal oxidation of natural rubbers from Hevea brasiliensis (pale crepe and smoked sheet) and Parthenium 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 ( E a ) were 16–17, 18–19, and 23–24 kcal/mole for the Borchardt‐Daniels, Kissinger‐Ozawa, and Jander models, respectively.