Phase morphology and surface properties of moisture cured polyurethane-urea (MCPU) coatings: Effect of catalysts

Effect of catalysts on curing behaviour, phase morphology and surface properties of a moisture cured polyurethane-urea (MCPU) coating has been studied. The prepolymer, prepared by capping hydroxy terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI), was cured with moisture using different urethane catalysts at 30 °C and relative humidity of 60%. Fourier transform infrared spectroscopy (FTIR) was used to monitor the curing process. Gel fraction studies through solubility method, show catalyst induced shortening of induction period for gelation and increase in gel fraction. Effect of catalysts on phase morphology of the MCPU was evaluated by X-ray diffraction, small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). The results show that the heat of fusion and interdomain distance of hard segments are influenced by the choice of catalysts. The effect on surface properties was evaluated by FTIR-ATR and contact angle goniometry. The type of H-bonding interaction was identified by deconvolution of the FTIR spectra. The results show that the surface polar group concentrations increase with increasing efficiency of the catalysts. Consequently there is a clear observation of catalyst induced surface energy changes of the MCPU.