Chemorheology of thermosetting resins. II. Effect of particulates on the chemorheology and curing kinetics of unsaturated polyester resin

The effect of particulates on both the rheological properties during cure and the curing kinetics of unsaturated resin has been investigated. For the investigation, a general‐purpose unsaturated polyester resin was used, with calcium carbonate and clay as inorganic particulates and high‐density polyethylene powder as organic particulates. It has been found that, as the particulate content increases, the resin/particulate mixture gives rise to shear‐thinning behavior and the rate of cure increases. It has also been found that the CaCO3 particles helped control shrinkage during cure when the material was subjected to steady shear deformation and that the gel time tη∞ is shorter for mixtures of resin and particulates than for the neat resin alone. Differential scanning calorimetry (DSC) is found useful for determining the curing kinetics of resin/particulate mixtures. We have combined rheological and DSC measurements to obtain a correlation between viscosity and the degree of cure during isothermal curing operations.