Kinetic rate equation combining ultraviolet‐induced curing and thermal curing. I. Bismaleimide system

Abstract

A novel and general kinetic rate equation combining ultraviolet-induced (UV-induced) curing and thermal curing was successfully derived from the conventional thermal-kinetic rate equation. This proposed novel kinetic rate equation can be applicable to the curing system either simultaneously or individually by UV-induced and thermal cure methods. This general kinetic rate equation is composed of the reaction order n, activation energy E a , curing temperature T, energy barrier of photoinitiation E Q , intensity of UV radiation Q, concentration of photoinitiator [I], and a few other parameters. The proposed equation was supported by experimental data based on the curing systems of 4,4 0 -bismaleimidodiphenylmethane (BMI) and 2,2-bis(4-(4 maleimido phenoxy) phenyl propane (BMIP). The BMI and BMIP systems were isothermally cured at various temperatures, or simultaneously cured with varying intensity of UV radiation (wavelength 365 nm). Conversion levels for the various cured samples were subsequently measured with a FTIR spectrometer. The reaction order n ¼ 1.2, activation energy E a ¼ 40,800 J/mol, and E Q ¼ 7.5 mW/cm 2 were obtained for curing BMI system. The reaction order n ¼ 1.3, activation energy E a ¼ 53,000 J/mol, and E Q ¼ 9.1 mW/cm 2 were obtained for curing BMIP system. The values of n and E a in the same curing system (BMI or BMIP) are irrespective of the curing method (either simultaneously or individually by UV-induced and thermal cure methods). The salient results of this study show that UV radiation only enhances the initiation rate and UV ration do not influence the activation energy E a . The experimental results are reasonably well represented by these semi-empirical expressions.

Asymmetric bismaleimide-based high-performance resins with improved processability and high Tg over 400 °C

“…To better understand the curing kinetics and determine the curing condition of the resins, a universal equation (3) is proposed here, 30…”

Effect of chemical structure on the crosslinking behavior of bismaleimides: Rheological study

“…There are several reports for homopolymerization of BMI and their structural effect that leads to crosslinking [1,3,4,7,8,24,25].…”

“…Dynamic mechanical analysis and rheometry have been used in many studies on crosslinking behaviors of thermoset polymers [23,[27][28][29][30][31][32][33][34][35][36][37][38][39][40]. For BMIs, however, the focus of most studies have been thermal or mechanical properties of the mixtures with other resins [25,[41][42][43][44], not of BMI resin alone. There are chemorheological studies involving the BMI resins [45][46][47][48][49][50][51], where BMI was usually used to enhance the composite properties [47,[49][50][51][52], and hence very few reports are available for neat bismaleimide system [39,45,46,48].…”