How Increasing Amounts of Trimerization Catalyst Impact the Formation, Isocyanurate Content, and Microstructure of Poly(urethane-isocyanurate) Rigid Foams

This study investigates the effect of trimerization catalyst (mainly composed of potassium ethyl hexanoate) content (0.5–6 pphp) on the kinetics, chemical properties, and cellular morphology of poly­(urethane-isocyanurate) rigid (PIR) foams. Increasing the trimerization catalyst content was found to accelerate the foaming process since all its characteristic times (cream time, gel time and tack-free time) were found to decrease (Δt gel ∼ −85%). Increasing the trimerization catalyst content was also found to significantly increase the maximum temperature reached during foaming, from 122 to 162 °C. ATR-FTIR spectroscopy analysis of the foam samples demonstrated that increasing the trimerization catalyst level significantly increased the isocyanurate content of the PIR matrix, which corroborated the reduction of nonreacted isocyanate. Accelerating the chemical reactions was also found to decrease the foam density and the cell height significantly (Δρf ∼ −18% and Δh ∼ −47%, respectively), thus increasing the cell population density by more than a factor of 15 through the reduction of cell coarsening and Oswald ripening. Open cell content was kept very low with a value under 4% for all catalyst contents.