Cure kinetics analysis and simulation of silicone adhesives

Abstract

A nonlinear transient heat transfer finite element model based on commercial finite element software, ABAQUS, is developed to simulate the curing process of silicone adhesive. The curing reaction process and specific heat of the silicone adhesive were investigated using a differential scanning calorimetry (DSC) to obtain material parameters for numerical simulations. Curing reaction kinetics was derived. Using the user subroutine HETVAL of ABAQUS, temperature distributions inside silicone can be evaluated by solving the heat conduction equations including internal heat generation produced by curing reactions. Good agreement between experimental data and numerical analysis by ABAQUS is obtained. IntroductionSilicone materials are well established products used in many applications. For electronics applications, silicone adhesives have demonstrated good performance. They have a high degree of flexibility to significantly increase the reliability and life of the devices because of the stressrelieving properties. They can also maintain the stressrelieving nature over a wide temperature or humidity range.The physical, chemical, and mechanical properties of the polymer are significantly affected by the curing behavior. The silicone adhesive requires the proper temperatures and time to achieve full cure and the best properties. Thus a thorough understanding of the vulcanization mechanism is desirable for better control of the curing process of silicone adhesives.The silicone adhesive studied in this work is a thermally curable, addition-curing, two-part, LTV silicone rubber. A hydrosilylation reaction will happen when sufficient heat is applied. Assuming that each cross-linking can releases the same amount of energy, the heat released in curing reaction can be utilized to monitor the curing process. Differential scanning calorimetry (DSC) technology is very capable of measuring thermal characterization of many materials, especially polymers [1,2,3,4].There have been many studies on the modeling or simulation of curing process of polymers [5,6,7,8]. In these works, the thermal properties in the cure circle were calculated mostly with one-or two-dimensional finite difference method. Finite element analysis was used just in recent years. The numerical software people used to study the curing process were the developed special-purpose or general-purpose software, just like ANASYS and ABAQUS. The internal heat generation produced by cure reactions can