On the use of DSC and DMA to characterize the degree of mixing of IPNs processed by RIM

Abstract

In Reaction Injection Molding (RIM), the degree of mixing is governed by the Reynolds number (Re) of the streams. Dimensional analysis predicts the mix quality to vary as (Re) − 9 4 . Past experiments at MIT showed that mixing did follow this relationship. The mixing theory is based on the hypothesis that the large scale mixing of the fluid components always occurs at high Reynolds numbers. On the other hand, the small scale of segregation of the mixture depends on the relative size of the turbulent eddies once the Reynolds number exceeds the critical value for the laminar/turbulent transition (Re ≈ 50). There were, however, no experimental values to predict these small scale features. Recent experiments have indicated that in the processing of Interpenetrating Polymer Networks (IPN) by RIM, the physical properties of the resulting alloys are highly dependent on the reaction kinetics and the degree of mixing. At high Reynolds numbers, thermal and dynamic mechanical measurements provide evidence of interphase mixing by shifts in the transition temperatures of the individual components.