In this paper, the curing of an unsaturated polyester resin catalysed with methyl ethyl ketone peroxide (MEKP) and cobalt octoate as the promoter, is studied at different heating rates. Given the non-symmetrical shape of differential scanning calorimetry (DSC) curves, it has been assumed that they would represent two independent reactions. The objective of this work has been to obtain a set of kinetic parameters for each DSC peak, which describe the overall cure process, using an empirical kinetic model of the form: da ¼ yk1 f (a1 ) þ (1 ¹ y)k2 f (a2 ) dt where y is the fraction corresponding to the heat released during the first reaction, and k i represents the rate constant for each process whose temperature dependence is an Arrhenius-type equation. With regard to f(a), two different kinetic functions have been employed: (1 ¹ a) n and a m(1 ¹ a) n. The corresponding software to compute the degree of conversion a 1 and a 2, and the kinetic parameters, has been developed. The kinetic parameters obtained considering two independent reactions and an autocatalysed function f(a), fit better than the DSC experimental data (da/dt,T) exp, than those obtained when a single kinetic process is considered. The activation energies for each process are in accordance with tabulated values for typical free-radical polymerizations, induced by redox and thermal decomposition of the peroxides.
Посилання на статтю:
Kinetic analysis of an asymmetrical DSC peak in the curing of an unsaturated polyester resin catalysed with MEKP and cobalt octoate / J.L. Martı́n // Polymer. – 1999. – N 40. – P. 3451–3462.