Vinyl ester resins with varied acid values (11, 22, 32, 38 and 48mg KOHg-1 solid) were prepared by reacting an epoxy novolac resin with methacrylic acid. The curing and decomposition behaviour of these resins containing styrene as reactive diluent (40%w/w) and benzoyl peroxide (2phr) as initiator were studied by d.s.c, and t.g.a. The activation energy and frequency factor for the curing reactions calculated by the Ozawa method were found to increase from 17 to 24 kcal mol-1 and 1.2 x 101 o to 6.6 x l0 t 3 min-1, respectively, with increase in the acid value of the samples. An isothermal temperature for the curing of all the resins was selected from the d.s.c, scans and at that temperature the cure time was found to increase with the acid value of the resins. The cured product with the lowest acid value was found to be the most thermally stable and a lifetime of 16.58 years at 400°C was estimated. The activation energy and frequency factor for the decomposition reactions, calculated by the Coats and Redfern method, decreased from 24 to 17.8 kcal mol-1 and 1.05 x 10 6 to 1.5 x 104min - 1, respectively, with increase in the acid value from 11 to 48 mg KOH g- t solid.
Посилання на статтю:
Curing and decomposition behaviour of vinyl ester resins / B. Gaur and J. S. P. Rai* // Polymer. – 1992. – Vol 33. – P. 4210-4214.