Chemical shrinkage and diffusion-controlled reaction of an epoxy molding compound

A methodology for the study of cure kinetics of a highly filled epoxy moldi ng compound is presented. An equation relating the glass transition tempera ture-conversion relationship was first established. The degree of conversio n can then be estimated when the calorimetric method is inadequate in measu ring the heat of reaction in the diffusion-controlled regime. The cure reac tion is modeled as a reaction of shifting order: it first reacts autocataly tically and later switches into diffusion control. The reaction in the diff usion-controlled regime is very slow and is modeled by an nth order kinetic equation. Both the linear coefficients of thermal expansion above and belo w the glass transition temperature decrease linearly with degree of convers ion. Based on this linear coefficient of thermal expansion-conversion relat ionship, it is found that chemical shrinkage is an important factor that ca uses interfacial stresses when the epoxy molding compound adheres to a subs trate of different materials. (C) 2000 Elsevier Science Ltd. All rights res erved.