Advances in HFC245fa Formulations and Processing

Abstract

Most of the US appliance industry has been working with new foam systems since last year. Following the phaseout of HCFC141b, zero ODP blowing agent HFC245fa (1,1,1,3,3 penta-fluoropropane) has been chosen by the majority of appliance manufacturers. However, the transition to HFC245fa has raised a few questions. Foam systems based on HFC245fa have handling requirements and performance characteristics that are different from HCFC141b. HFC245fa has a boiling point of 59 F (15 C). This is much lower than the boiling point of HCFC141b, which is 90 F (32 C). The lower boiling point is the primary reason why HFC245fa foam systems have significantly different processing characteristics. The impact of these processing differences (as well as some formulating trends) are described in this paper. A driving force behind this program is the desire to optimize foam performance and reduce foam cost through the determination of the required HFC245fa level. HFC245fa is an excellent blowing agent; however, the high cost of this product has altered the economics of appliance manufacturing.In order to minimize the cost, it is extremely important to determine ways to utilize HFC245fa most efficiently. One way to minimize foam cost is to insure maximum retention of the HFC245fa in the polyol blend. A study was performed to determine the optimum storage and handling procedures for HFC245fa. Another way to reduce cost is to substitute water for equivalent reductions in HFC245fa loading. Water is typically used as a source of a chemical blowing agent through the generation of CO2, by way of the water–isocyanate reaction. With blowing agents such as HCFC141b, there is a general trend that shows a decrease in the thermal insulation of the foam as water levels are increased. It is important to determine whether HFC245fa behaves in a similar fashion. These issues result in opposing objectives that require optimization, since it would be desirable to reduce HFC245fa loadings from a cost standpoint, but at the same time manufacturing demands require a certain level of insulation performance from the foam. As a means of understanding the balance between cost reduction and thermal insulation, this study considered a range of CO2 levels in order to determine the amount of HFC245fa reduction that can be achieved while maintaining superior insulation performance. The study also took into account the effect of process variations on an optimized HFC245fa system. It was believed that the set of process conditions that were developed for HCFC141b might need to be adjusted when using HFC245fa. The parameters that were evaluated included chemical temperatures, mix pressures, and machine throughputs. This work has led to the identification of a number of interesting findings. With the results of this study, the foam technologist has a better understanding of the variables that need to be selected in order to provide the best balance of processing and foam performance for HFC245fa appliance systems. In view of the relatively high cost of HFC245fa, such an optimization process is necessary in order to fully exploit the technical possibilities of this new blowing agent.