| Reaction injection molding (RIM) is a relatively new process for high speed production of polymer parts directly by fast polymerization of low viscosity reactants. Two important processes, polymerization and phase separation, have to be accomplished in situ within the mold during polyurethane RIM. The goal of this thesis work is to obtain a fundamental understanding of the property development during fast polyurethane RIM polymerization. Efforts have been focused on monitoring the time-dependent behavior of phase separation and its interaction with polymerization kinetics.;Fourier transform infrared spectroscopy (FT-IR) is used to simultaneously obtain information of phase separation and polymerization. In addition, dynamic mechanical spectra (DMS) is used to measure the rheological changes during polymerization. A portable Micro-RIM machine is interfaced with a FT-IR spectrometer and a Rheometrics System IV rheometer. Effects of catalyst concentration, reaction temperature, hard segment content, and type of isocyanate and polyol on phase separation dynamics and polymerization kinetics are investigated. Characterization of the as polymerized materials clearly demonstrates the importance of interplay of phase separation and polymerization on the final physical properties.;Moldability diagrams generated from the FT-IR and DMS data are convenient to illustrate the relation between phase separation dynamics and polymerization kinetics. The demolding results can be successfully related through these moldability diagrams to the processing conditions (catalyst level, mold temperature, and demold time).;Besides phase separation dynamics and polymerization kinetics, this thesis work also contributes to the understanding of thermal degradation of urethane bonds, polymorphism of MDI/BDO crystalline structures, and effect of urea versus urethane linkages on polymer properties. |
