Kinetics of the curing reaction of unsaturated polyester resins catalyzed with new initiators and a promoter

In this article, the curing of unsaturated polyester resins catalyzed with a promoter [cobalt(II) octoate] and free-radical initiators is presented. The new initiators were formed by the oxidation process of ethyl methyl ketone or cyclohexanone with hydrogen peroxide and the mixture of solvents containing hydroxyl groups. As a reference, a typical curing system containing ethyl methyl ketone hydroperoxide (Luperox) and the promoter was used. The differential scanning calorimetry runs were performed at different heating rates. The experimental data were fitted with the empirical kinetic model. First, the kinetic parameters (activation energy, frequency factor, and reaction order) were obtained with a single reactive process and with the nth-order reaction f(alpha), the nth-order reaction f(alpha) with autocatalysis, and the first-order reaction f(alpha) with autocatalysis. Second, two or three different reactive processes with the nth-order reaction f(alpha) for each step were used. The obtained values of the activation energies for the curing of the unsaturated polyester resins with the free radical initiator-cobalt(II) salt catalytic system were in the range 40-60 kJ/mol for the polymerization initiated by the redox decomposition of the initiators and 80-90 kJ/mol for the polymerization initiated by the thermal decomposition of the initiators at high temperatures. (c) 2006 Wiley Periodicals, Inc.