Cure Kinetics Modeling of a High Glass Transition Temperature Epoxy Molding Compound (EMC) Based on Inline Dielectric Analysis

Abstract

We report on the cure characterization, based on inline monitoring of the dielectric parameters, of a commercially available epoxy phenol resin molding compound with a high glass transition temperature (>195 °C), which is suitable for the direct packaging of electronic components. The resin was cured under isothermal temperatures close to general process conditions (165–185 °C). The material conversion was determined by measuring the ion viscosity. The change of the ion viscosity as a function of time and temperature was used to characterize the cross-linking behavior, following two separate approaches (model based and isoconversional). The determined kinetic parameters are in good agreement with those reported in the literature for EMCs and lead to accurate cure predictions under process-near conditions. Furthermore, the kinetic models based on dielectric analysis (DEA) were compared with standard offline differential scanning calorimetry (DSC) models, which were based on dynamic measurements. Many of the determined kinetic parameters had similar values for the different approaches. Major deviations were found for the parameters linked to the end of the reaction where vitrification phenomena occur under process-related conditions. The glass transition temperature of the inline molded parts was determined via thermomechanical analysis (TMA) to confirm the vitrification effect. The similarities and differences between the resulting kinetics models of the two different measurement techniques are presented and it is shown how dielectric analysis can be of high relevance for the characterization of the curing reaction under conditions close to series production.

Universal Cure-Induced Shrinkage Model Applied to an Epoxy Amine as a Method to Optimize Composite Processing Time, Shrinkage, and Residual Stress

“…In this case, the total enthalpy was 435 J/g. The two-parameter Kamal–Sourour autocatalytic model described in eq has proven to be effective in modeling a wide range of epoxy-based resins, − where k 1 and k 2 are the rate constants and m and n serve as the overall reaction orders. Equation describes a modification of the model to include a parameter that takes account of the onset of a diffusion-controlled mechanism once vitrification has occurred, referred to as the Chern and Poehlein optimization parameter: . where C is a constant, α is the fractional cure conversion, and α c is the critical conversion, defined as the conversion at which diffusion control begins to dominate the reaction.…”

Effectiveness and Productivity Improvement of Conventional Pultrusion Processes

“…To describe the rate of resin reaction, the Kamal–Sourour curing kinetic model [ 33 , 34 , 35 ], which in the best way approximates the results of differential scanning calorimetry (DSC) tests, was chosen: where J/mol·K is the universal gas constant, and are the frequency factors, and are the activation energies, and and are the orders of the reaction. It is necessary to note that the Kamal–Sourour reaction model combines autocatalytic behavior with an n -th-order reaction model and besides the first rate constant and the exponent describe the n -th-order reaction and the second rate constant and the exponent express the autocatalytic contribution of the reaction.…”

“…The developed methodology was successfully applied for optimization of conventional pultrusion processes, producing profiles with different cross sections (Figure 2) and made of glass fibers and the following thermoset resins: polyester C-L ISO 112G, vinyl ester Crystic VE 676-03 [31], and epoxy Resoltech 1401+1407+AC140 [32]. The thermal properties of corresponding tool materials (Table A1) were taken from the handbooks and datasheets, but the properties of composite materials (Table A2) were measured experimentally with the lamped properties evaluated by the rule of mixtures [24]: To describe the rate of resin reaction, the Kamal-Sourour curing kinetic model [33][34][35], which in the best way approximates the results of differential scanning calorimetry (DSC) tests, was chosen:…”

In Situ Thermoset Cure Sensing: A Review of Correlation Methods

“…A similar equation for degree of cure was calculated from the ion viscosities in accordance with Equation (19): in which the subscripts indicate the minimum and maximum ion viscosities measured during the cure. Franieck et al evaluated Equation (19) for a silica-filled epoxy in which cure was monitored using a tool-mounted monotrode dielectric sensor [ 87 ]. The results from this analysis were compared to the degree of cure calculated from DSC, with limited success.…”