The use of insulating products in the building envelope is defined by many criteria. The specified R-value or k-factor for the structure is an essential component of most specifications. The industry has traditionally reported the R-value measured at a mean temperature of 75°F for use to calculate insulation requirements for the building envelope. With improvements in instrumentation, it is now possible to specify insulation based upon the actual use temperatures for a given building or region. This paper compares the performance of insulating products over a variety of mean temperature ranges including a discussion of measurement methods.
The effective use of insulation is key to energy conservation. The effectiveness of insulation is dependent upon many factors. In the case of rigid foam insulation a key factor is the blowing agent used. Industry evaluations have shown that HFC-245fa produces foams with the highest insulation value of any HCFC-141b alternative-blowing agent in the construction market. Meeting the market needs is critical to the success of any new product. Today’s insulation specifiers are not only concerned about energy savings but also cost. Chemical and manufacturing changes can have a significant effect on product cost. The higher vapor pressure of HFC-245fa and its potential impact on packaging has also been a concern to the spray foam industry. This paper contains the latest results about the use of HFC-245fa foam systems co-blown with water, which meet the needs of the spray foam market. They are cost effective, produce foams with low k-factors, good physical properties, and can be stored and shipped in existing drums. This will allow applicators and manufacturers to safely use existing equipment without significant modifications or safety concerns. HFC-245fa and water used as co-blowing agents provide a wide range of benefits in spray foam. Since less HFC-245fa is used, the vapor pressure is lower, and the cost of the system is reduced while improving the physical properties of the foam. There is however an increase in k-factor. We have determined also that the addition of low levels of •-methyl styrene to a spray foam polyol blend lowers the vapor pressure of the polyol blend and enhances the k-factor of the foams produced. This allows the user to optimize k-factor while lowering the cost. Data from laboratory evaluations of these blends are presented. This paper also includes a discussion of the cost of these blends from a chemical, manufacturing and performance perspective. We consider HFC-245fa/water co-blown spray foam to be a quality, cost effective and safe alternative to HCFC-141b blown foams in the future.
Because of continuing environmental concerns about ozone depletion, regulatory mandates have been established that require the phaseout of compounds with any potential to deplete the ozone layer, including HCFC-141b. These regulations vary from country to country, but in the U.S., for example, HCFC-141b will be phased out in less than a decade. Although there are several potential options for replacement blowing agents, many applications will continue to require a liquid, non-flammable blowing agent designed to produce foams with low thermal conductivity using traditional processing techniques. The most promising class of materials to fill this need are liquid HFCs. AlliedSignal is committed to supplying a liquid HFC blowing agent to the foam industry. At the 1994 Polyurethane World Congress, AlliedSignal announced that HFC-245fa (1,1,1,3,3-pentafluoropropane) was our primary candidate for a liquid HFC "third generation" blowing agent to replace HCFC-141b. This molecule was selected after a rigorous screening process in which several hundred candidates were ranked using physical properties, flammability characteristics, performance as a blowing agent, economics, environmental acceptability, and anticipated toxicity as selection criteria. HFC-245fa was found to offer the optimum combination of these attributes. In order to fully qualify this or any other material as a foam blowing agent, however, much more extensive work is required in all these areas. Additionally, customer validation and feedback is critical at every step in the process to ensure commercial viability and ultimate acceptance in the rigid foam market. This paper provides an update on the continuing HFC-245fa development program being conducted by AlliedSignal. The physical, environmental, and flammability properties of HFC-245fa are reviewed. Of particular note is that the flammability of HFC-245fa has been extensively tested by several ASTM test methods and the product's non-flammability has been confirmed. An update of the toxicity testing program for HFC-245fa is given. Results to date are very encouraging. The acute testing program is nearly complete and the results suggest that this material has a very low order of acute toxicity. This acute testing, however, does not provide a guarantee of success in full-scale toxicity tests. Full scale toxicity testing of HFC-245fa in several repeated dose studies is scheduled to begin soon. An important property of any blowing agent is its stability, both thermal and chemical. HFC-245fa has previously been shown to exhibit excellent thermal stability up to 200°C neat and in the presence of water, aluminum, and/or stainless steel [1]. Further testing has been conducted to determine the thermal stability of HFC-245fa in the presence of cold rolled steel under a variety of conditions. HFC-245fa continues to show excellent thermal stability characteristics under a variety of conditions. Three aspects of chemical stability are discussed. The first is the stability of the blowing agent in the presence of other common polyurethane foam raw materials and blends. Related to this is the stability of formulated "B" components after extended storage periods as measured by changes in system reactivity over time. The third is the stability of the blowing agent during the foaming reaction as determined by measuring levels of decomposition products, if any, in the foam's cells. The results of our preliminary investigations in these three areas are very encouraging. A major difference between HFC-245fa and HCFC-141b is their boiling points, 59°F for HFC-245fa vs 89°F for HCFC-141b. The implications of the lower boiling point and correspondingly higher vapor pressure of HFC-245fa vs HCFC-141b in two important areas, storage/handling and foam properties have been previously discussed [1]. Although the higher vapor pressure of HFC-245fa may require some small modifications to the way the material is handled, the impact of this lower boiling point on low temperature dimensional stability and thermal conductivity appears to be very positive. The acceptability of any blowing agent candidate will ultimately be based on performance. The results of both internal and customer evaluations involving machine and hand mix studies in a variety of formulations are presented. The viability of HFC-245fa as a foam blowing agent has been demonstrated. Work has begun to optimize both formulations and processing conditions to achieve optimum performance from HFC-245fa. It is anticipated that these data will provide a starting point from which foam formulators can begin their proprietary formulation development activities. In addition to producing foams with k-factors approaching those of HCFC-141b blown foams, our evaluations to date indicate that the intermediate boiling point of HFC-245fa (lower than a traditional liquid blowing agent but higher than a true gaseous blowing agent) results in foams that have the excellent uniformity and physical properties of traditional pour foams, but that also have the isotropic cell structure and excellent flow characteristics most often associated with froth foams. Results of an AHAM sponsored trial which evaluated the performance of HFC-245fa blown foam in a refrigerator cabinet are presented. The results are very positive. Foam processing was judged to be excellent and refrigerator energy consumption was nearly as good as that of refrigerator cabinets filled with HCFC-141b blown foams. Data are provided on the k-factor aging characteristics of HFC-245fa blown appliance and boardstock foams. Thermal conductivity of HFC-245fa blown foams as a function of mean temperature is also discussed. The paper concludes with a discussion of AlliedSignal's plans for the continuing development and commercialization of HFC-245fa as a blowing agent for rigid polyurethane and polyisocyanurate foams.
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 CFC's to HCFC's and the industry will soon see another transition from HCFC's 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.
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