Spiral Flow Modelling of a Filled Epoxy-Novolac Molding Compound.

The spiral flow of a thermosetting molding compound is a measure of the combined characteristics of fusion under pressure, melt viscosity, and gelation rate under specific conditions (ASTM D 3123). In this work the spiral flow of a filled epoxy-novolac system was measured at different temperatures and pressures. The reaction kinetics were determined by DSC, and the dependence of viscosity on temperature and conversion was analyzed with a parallel-plate rheometer. The shear-rate dependence of the viscosity was studied using an unreactive compound which is otherwise identical in composition to the molding compound. The material shows a shear thinning behavior with a power-law index of 0.83. The kinetic and rheological information was used in a finite-difference computer program to simulate the spiral flow. The spiral flow length predicted by the model agrees well with the experimental measurements at different temperatures and pressures.