Abstract
When expanded with CFCs, rigid polyurethane foams display exceptional thermal insulation properties. The imminent phase-out of CFCs due to their environmental impact, however, has produced intensive research programmes throughout the polyurethanes industry. These aim to develop technologies, based on environmentally acceptable blowing agents, which produce foams with equivalent insulation performance to CFC 11 systems.
HCFC 22 has been considered as a possible alternative to CFC 11 because of its lower environmental impact. The gas's low boiling point of -40°C, however, results in processing problems which lead to distorted foam morphology, bad initial thermal conductivity X. values and rapid X value ageing.
The wide availability of HCFC 22, however, coupled with its low toxicity, non-flammability and high affinity to both polyol and isocyanate make it a strong candidate for replacing CFC 11, if the above problems can be overcome.
This paper reports developments with a novel technology based on HCFC 22. The technology results not only in improved X. value performance in rigid polyurethane foams, but also allows high HCFC 22 loadings whilst retaining a fine celled structure.
These higher loadings result in further improvements in thermal conductivity, better than production values actually obtained when using reduced CFC 11 systems. Different aspects of this novel technology, including lambda value performance, energy consumption data and relevant physical properties are discussed.
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