Simulation of liquid physical blowing agents for forming rigid urethane foams

A computer-based simulation for rigid polyurethane foam-forming reactions was compared with experimental data for six blowing agents including methyl formate and C5-C6 hydrocarbons. Evaporation of blowing agent was modeled as an overall mass transfer coefficient times the difference in activity of the blowing agent in the gas foam cells versus the resin walls of the cells. Successful modeling hinged upon use of a mass transfer coefficient that decreased to near zero as the foam resin approached its gel point. Modeling on density agreed with experimental measurements. The fitted parameters allowed for interpretations of the final disposition of the blowing agent, especially, if the blowing agent successfully led to larger foam cells versus being entrapped in the resin. The only component-specific fitted parameters used in the modeling was the activity coefficient that was lower for methyl formate than the value used for hydrocarbons. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42454.