Robert Christian Parker

Evaluation of Next Generation Blowing Agents

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.

Utilization of HFC-245fa in the construction industry

The effective use of insulation in both commercial and residential buildings is the key to energy conservation. The effectiveness of an insulation is dependent upon many factors. If the insulation is a foam plastic, the blowing agent used in the insulation is critical to its performance. There has been a transition in blowing agents over the last decade from CFCs to HCFCs and the industry will soon see another transition from HCFCs to a third generation blowing agent. The exact timing of these transitions is dependent upon the Montreal Protocol national and local regulations. Each transition in blowing agents requires modifications to the manufacturing process for the foam products. AlliedSignal is dedicated to providing an HFC blowing agent to the construction industry and has identified HFC-245fa (1,1,1,3,3-pentafluoropropane) as our third generation blowing agent. Since 1994, we have published a series of papers on the development of this blowing agent. This paper discusses some of the key considerations required in making the transition from HCFC-141b to HFC-245fa in areas of polyisocyanurate boardstock and spray foam. It also discusses progress made in the application of HFC-245fa in bunstock and pour in place panel applications. It will discuss the progress in areas such as raw materials and formulation optimization, possible equipment and processing parameters changes required to optimize performance, and a general discussion of foam properties, including flammability, in comparison to HCFC-141b blown foams. It will focus on providing the information which board and system manufacturers and spray foam applicators will need to make a successful transition. This includes information on gasket compatibility, gloves, system vapor pressures, system packaging and shipping requirements and product performance.

HFC-245fa as a Blowing Agent for the Appliance Industry

HFC-245fa (1,1,1,3,3-pentafluoropropane) has been under development by AlliedSignal since 1994 as a potential replacement for HCFC-141b in blowing agent applications. During 1996, a great deal of work took place that compared the physical properties of appliance foams prepared with HFC-245fa versus other blowing agents. During 1997, it is anticipated that ongoing performance optimization work will enable appliance manufacturers to conduct plant trials using HFC-245fa as the blowing agent. The domestic refrigerator appliance industry is under a time constraint to make a transition to a third generation blowing agent, such as HFC-245fa, by January 2003. In addition to the phase out of HCFCs, Department of Energy regulations will mandate an increase in the energy efficiency of refrigerators effective July 1, 2001. Needless to say, the development time for the appliance industry is short. Further optimization studies will enhance the insulation value and physical properties of foams blown with HFC-245fa. Development work is also being performed that examines the overall system, that is, the interaction of HFC-245fa foam blown into the walls of a refrigerator. This paper will discuss the results of a freeze stable density study using HCFC-141b and HFC-245fa as blowing agents. Results from a surfactant screening study that examines flowability will be reviewed. In addition, modeling of blowing agent diffusion into a refrigerator will be discussed. This work is part of a continuing effort by AlliedSignal to develop a blowing agent replacement for HCFC-141b that meets the needs of our customers well into the future.