Nonisothermal Decomposition Kinetics of Chromium-Polyacrylate Complexes Prepared from Aged Cr(iii) Solutions

Thermogravimetric studies of poly(acrylic acid) (PAA) and its chromium-polyacrylate complexes prepared from Cr(III) solutions aged for different times were undertaken. Six kinetic methods were used to investigate the thermal decomposition behavior of these materials. The applied methods were the Coats-Redfern, Horowitz-Metzger, MacCallum-Tanner, van Krevelen, Madhusudanan-Krishnan-Ninan, and Criado methods. The activation energy values obtained with the Coats-Redfern, Horowitz-Metzger, and MacCallum-Tanner methods were in good agreement with one another, and those obtained with the van Krevelen and Madhusudanan-Krishnan-Ninan methods were found to be 10-20 kJ/mol larger. The apparent activation energies increased for the complexes prepared from Cr(III) solutions aged for longer times. An analysis of the experimental results suggested that the actual decomposition mechanisms of PAA and the metal-polymer complexes were a Dn deceleration type