The Effects of Water as a Partial Blowing Agent for Rigid PUR and PUR/PIR Foams

Abstract

Trichlorofluoromethane, CFC-11, is the predominant blowing agent used for rigid PUR and PUR/PIR insulation foams. The low thermal conductivity of CFC-11 provides these products with excellent insulation properties. But, it is now known that future supplies of CFC-11 may be limited and possibly eliminated as a consequence of international regulation. New, hydro-chloro-fluorocarbons (HCFCs) are under development and evaluation, with HCFC-141b and HCFC-123 emerging as the front runners to replace CFC-11. However, neither product is ex pected to be commercially available for several years. In the meantime, it is expected that regulation, in combmation with industry growth, will cause a real shortage of CFC blowing agent available for foam blowing.

Water blowing of polyurethane foams has been used to a limited extent for a num ber of applications. Therefore, it was concluded that increasing the level of water blowing in PUR and PUR/PIR foams offered the most promising short term solution to extending future supplies of CFC-11. This paper discusses the use of water blow ing for a number of rigid foam applications including appliances and lamination boardstock. Information obtained from both laboratory and commercial production experience is presented. It is shown how careful optimization of all formulating ele ments involved can, in some cases, result in no loss in the foam insulation efficiency even with up to 40% reduction of CFC-11 usage.