Performance of HFC-245fa in Integral Skin Foam Applications

Hydrochlorofluorocarbons have been banned in the US from use in integral skin applications since January 1, 1994, with the exception of automotive safety application, which was granted an extension until January 1, 1996. In Europe, HCFC-141b was banned from use in integral skin foam after January 1, 2000, except for safety applications. Rules for the continued use of HCFC-141b for integral skin foam for safety applications are currently under review in Europe. Other blowing agents, such as CO 2 (water), HFC-134a and hydrocarbons, are currently being used with varying degrees of success. CO 2 (water) based integral skin foams require higher foam densities and produce poor skin quality. HFC-134a has been added to these formulations to minimize pinholes associated with CO 2 (water) blown foams. In some instances, CO 2 (water) also requires the use of more expensive pure MDI versus polymeric MDI to achieve desired properties. HFC-245fa (1,1,1,3,3-pentafluoropropane) has been evaluated by several foam manufacturers and shows promise as a potential blowing agent for integral skin foam applications. The physical properties of these foams are excellent, comparable to CFC-11 based foams, especially in the areas of skin quality and thickness. A CFC-11 based formulation was used to compare the physical properties of foams prepared using CFC-11 versus HFC-245fa. The resulting foam showed favorable properties in terms of skin thickness, skin quality and processing. The comparative work on CFC-11 and HFC-245fa produced some unexpected results. At the same weight percent loading of blowing agent in the resin, the free rise density of HFC-245fa blown foams was approximately one-half that of the CFC-11 based foams even though HFC-245fa and CFC-11 have very similar molecular weights. HFC-245fa has improved solubility in resin Premixes versus HFC-134a. HFC-245fa produces lower density foams compared to HFC-134a. At the same free rise density, HFC-245fa provides a skin 25 to 50 percent thicker than HFC-134a. HFC-245fa based integral skin foams also provide improved mechanical properties versus HFC-134a.