Investigation of effects of dibutyltin dilaurate on reaction injection molding polyurethane-urea kinetics, morphology and mechanical properties by in situ FTIR

The bulk catalyst effect of dibutyltin dilaurate (DBTDL) on the reaction of NCO respectively with OH and NH₂ was investigated in detail. The results showed that DBTDL had specific catalyst effect on the reaction of NCO with OH and no measurable effect on the reaction of NCO with NH₂. In situ Fourier transform infrared spectroscopy (FTIR) used in the reaction injection molding (RIM) process showed that with increasing the concentration of DBTDL, the formation rate of the soft segment became fast, and the order degree of urea carbonyls became worse. Meanwhile, more arrange manners of urea carbonyl were present. The bands at 1653, 1647 and 1637 cm⁻¹ were able to be detected at the low conversion. No hydrogen-bonded urea carbonyl available in the spectra at the beginning. The tensile-stress behavior showed that, with the increase of the DBTDL content, the interaction between polar groups became weak, while the virtual crosslinks also became weak. Although the break stress (d), 300‰δ and the hardness of elastomers decreased obviously, however, the tear strength, associated with the morphology of polyurethane-urea (PUU), showed the maximum when the DBTDL content was 2.63‰.