Progress in the Reduction and Elimination of the Use of CFCs in Rigid Polyurethane Foam

Abstract

There is a growing consensus that CFCs will be phased out by the year 2000. Finding other ways of blowing polyurethane foams whilst retaining their excellent insulation properties is the major technical challenge currently facing the polyurethanes industry. The most promising technical solution to date is the replacement of CFC 11, the principal blowing agent for rigid polyurethane foams, by either HFA 123 or HFA 141b. Both are proving to be viable alternatives.

Significant progress has already been made in reducing substantially the amount of CFC 11 needed for foam manufacture by using a dual-blowing approach – up to 50% of CFC 11 is replaced by an equimolar amount of carbon dioxide. This has been achieved by systems optimisation without compromising insulation values or other properties. Such systems are in production in the appliance industry in Western Europe and are now being commercialised in the USA and Far East. Similar technology has been developed for panels and laminates in the construction industry and systems are now being commercialised.

A variety of options to replace CFC 11 totally is under investigation. Complete blowing with carbon dioxide has several drawbacks, but has to be given further consideration. The development of a wider range of air-impermeable facing materials to eliminate rapid λ-value ageing is seen as a key technical requirement.

However, hydrofluoroalkane (HFA) products are seen increasingly by the polyurethanes industry as the most viable alternatives for polyurethane foam blowing. HFA 123 and HFA 141b have greatly reduced capabilities for ozone depletion and their global warming potentials are also significantly less than CFC 11. Since toxicity testing is not yet complete, commercial production of either product is unable to start before 1993, given the most optimistic progress. Short-term solutions are being developed for some markets before these alternatives are introduced, but availability of at least one of these HFAs is considered to be essential for polyurethane foam manufacture over a 30 to 40 year timescale.