Zero-ODP Blowing Agents for Polyurethane Foams

As we move toward final phaseout of chlorofluorocarbon blowing agents, new compounds and technologies are emerging to produce the polyurethane foams essential to so many products. In considering zero-ozone-depleting compounds that are currently available, the potential hydrofluorocarbon (HFC) candidates are gases at ambient conditions. Development programs are under way to understand feasibility and demonstrate use of one candidate, HFC-134a, to replace CFC-11. This paper summarizes basic data developed to support commercial process conversion from CFC-11 to HFC-134a. Topics include a comparison of physical properties, results of vapor pressure and solubility studies with different polyols, effects of different surfactants on HFC-134a solubility, confirmation of product stability in foaming applications, B-side system viscosity effects, and materials-of-construction compatibility data. With respect to processing, the paper summarizes experience developed in modifying equipment to handle higher B-side mixing and storage pressures and discusses effects of process settings on foam quality. Finally, the paper summarizes results of commercializing 134a/polyurethane foam systems for both insulating and non-insulating applications.