Rheo-kinetic changes in polyurea reaction injection molding

In order to conduct a quantitative analysis of the polyurea RIM process, a thorough understanding of the reaction kinetics and rheological changes during reaction is required. Since the system reacts too fast for most analytical instruments to be applied, a solution polymerization technique was used to slow down the reaction such that both kinetic and rheological information could be obtained. The results from the solution polymerization can also be applied to predict the behavior of polyurea in the RIM process. To study the composition effect, the ratio of aliphatic and aromatic diamine was varied from 70/30 to 10/90 by weight with equivalent moles of diisocyanate. In addition, non-segmented polyurea (i.e., T5000 and I1305 or aromatic diamines and I1305) were also studied. Experiments show that apparently different solvents affect the formation of hydrogen bonding in polyurea which in turn affects the phase formation, rheological changes and reaction kinetics. In order to apply solution polymerization data to predict the polyurea formation in the RIM process, an inert solvent should be chosen. Based on the experimental results shown and the work reported by other researchers, nitrobenzene seems to be a good choice.