A New Instrument for Measuring Isotropic Stress Development and Reaction Kinetics for Thermosetting Resins

摘要

We have developed a novel method for measuring the isotropic stress development in a thermosetting resin during cure and subsequent thermal cycling. We use a sealed stainless steel spherical pressure vessel to impose three-dimensional isotropic constraints. The strain at the outer surface of the vessel is monitored by strain gauges and the heat exchange between the vessel and a thermostat is measured by thermocouples. We can, thus, follow both the development of isotropic stress and the reaction kinetics during cure. Measurement of the isotropic stress as a function of temperature allows us to also obtain the product of the thermal expansion coefficient and the bulk modulus (αK) in both the glassy and rubbery (or liquid) states.