Unsaturated polyester-polyurethane IPN RIM materials

Abstract

An engineering analysis on the unsaturated polyester (UPE)-polyurethane(PU) interpenetrating polymer networks(IPN``s) was carried out for the UPE rich compositions and reaction injection molding(RIM) formulations. Fundamental studies of reaction kinetics, viscosity behavior, phase separation behavior mechanical properties, and computer simulations were conducted. The unsaturated polyester resin composed of phthalic anhydride, maleic anhydride, and propylene glycol was crosslinked with styrene monomer in the presence of methyl ethyl ketone peroxide(MEKPO) and cobalt naphthenate(Co. Na.). The polyurethane network was prepared by reacting poly(tetramethylene ether) glycol (PTMG), trimethylol propane(TMP), ad 4, 4``-diphenyl methane diisocyanate(MDI) using Co. NA. as a catalyst. The reaction kinetic model was established reflecting the interaction of constituent components through measuring the reaction exotherms of IPN``s by the differential scanning calorimetry(DSC). The results in reaction kinetics of IPN formation showed that there were complicated interactions between the two reactions in spite of different reaction mechanisms. It was revealed that the MDI and Co. Na. complex had a significant catalytic effect on the UPE reaction. However, the final conversion of UPE reaction decreased in the IPN by the cage effect of the PU network which restricted the diffusion of the styrene monomer. The intermediate reaction products having a certain conversion were prepared in order to obtain conversion dependence of viscosity. The proper rheological model describing the viscosity change during the reaction was established as a function of temperature and conversion. The composition dependence of blend viscosity showed that the Takayanagi``s model was adequate in heterogeneous blend region, but the logarithmic mixing rule was preferred in homogeneous region. The phase separation behavior during IPN formation was observed by light scattering and turbidity experimen...