Modeling and experimentation of polyol + blowing agent systems

Polyurethane foams are made by reacting a di-isocyanate molecule with a polyol in the presence of a blowing agent. Solubility of the blowing agent in the polyol plays an important role on the foaming nature of polyurethane. Traditionally, Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, etc., were used as the blowing agents. However, the Montreal protocol of 1987 classified most of the blowing agents being used to make polyurethane foam as ozone depleting and set forth a complete phase out of CFCs by year 2000 and HCFCs by year 2030.;This brought forward the need for the development of new environment-friendly blowing agents. Hydrofluorocarbons (HFCs) are being considered as the next generation blowing agent replacements for CFCs and HCFCs. Solubility of the blowing agent in the polyol is an important criterion in selecting a compound for blowing agent applications. The degree of foaming, cellular structure, and dimensional stability are all largely controlled by the solubility. Research is ongoing to determine a good model to describe polyol + blowing agent systems. The Sanchez-Lacombe (SL) Equation of State (EOS) and Statistical Associating Fluid Theory with Variable Range (SAFT-VR) EOS have been used in the past to determine the solubility of small molecules (like blowing agents) in the polymers (polyols), but unfortunately very limited experimental solubility data are available to evaluate the correlative ability of these EOS for these type of systems.;In this work, a degassed vapor pressure apparatus is designed to experimentally determine the solubility of HFC125, HFC152a, HFC143a, and HFC32 (blowing agents) in PluracolRTM 975, PluracolRTM 355, and TerolRTM 352 (polyols). From the results HFC152a is found to have good solubility in all three polyols, and from the solubility point of view, HFC152a + PluracolRTM 975 is found to be the best combination to produce polyurethane foam. HFC143a has been found to be the least soluble blowing agent in all three polyols. The structure of the blowing agent molecule and the hydroxyl groups of the polyol molecule are found to be the important factors in determining the solubility of the blowing agent in the polyol. The theoretical study indicates that SL-EOS is much more accurate than SAFT-VR EOS in correlating the solubility results. The binary interaction parameter of SL-EOS for all the systems did not deviate much from zero, proving it to be suitable for modeling polyol + blowing agent systems.