Rheological characterization of fast‐reacting thermosets through spiral flow experiments

The standard spiral flow test is normally used to assess the “moldability” of thermosetting materials. It is proposed that such tests can be modified and analyzed to yield rheological information as from a viscometer. Specifically, a “parameter‐identification” scheme is developed to determine the constants in a viscosity model by minimizing the difference between the outcome of spiral flow tests and the results of numerical simulations of these tests. The proposed scheme is particularly applicable to fast‐reacting thermosets for which typical viscometers cannot be used. Successful application of the scheme is demonstrated for a particular encapsulating epoxy material, where constants are obtained for a modified WLF equation viscosity model. These constants are used to predict the outcome of spiral flow experiments not involved in the minimization procedure. A favorable comparison between experiment and simulation occurs at most operating conditions. The method requires no elaborate equipment or delicate instrumentation.