How Increasing\nAmounts of Trimerization Catalyst Impact\nthe Formation, Isocyanurate Content, and Microstructure of Poly(urethane-isocyanurate)\nRigid Foams

This study investigates the effect of trimerization catalyst\n(mainly\ncomposed of potassium ethyl hexanoate) content (0.5–6 pphp)\non the kinetics, chemical properties, and cellular morphology of poly(urethane-isocyanurate)\nrigid (PIR) foams. Increasing the trimerization catalyst content was\nfound to accelerate the foaming process since all its characteristic\ntimes (cream time, gel time and tack-free time) were found to decrease\n(Δ<i>t</i><sub>gel</sub> ∼ −85%). Increasing\nthe trimerization catalyst content was also found to significantly\nincrease the maximum temperature reached during foaming, from 122\nto 162 °C. ATR-FTIR spectroscopy analysis of the foam samples\ndemonstrated that increasing the trimerization catalyst level significantly\nincreased the isocyanurate content of the PIR matrix, which corroborated\nthe reduction of nonreacted isocyanate. Accelerating the chemical\nreactions was also found to decrease the foam density and the cell\nheight significantly (Δρ<sub>f</sub> ∼ −18%\nand Δ<i>h</i> ∼ −47%, respectively),\nthus increasing the cell population density by more than a factor\nof 15 through the reduction of cell coarsening and Oswald ripening.\nOpen cell content was kept very low with a value under 4% for all\ncatalyst contents.