Abstract
Liquid hydrocarbons and hydrofluorocarbons (HFCs) are the leading zero ozone depletion potential (ODP) blowing agents being considered for rigid polyurethane foam insulation used in the construction industry. Different isomers of pentane, namely normal-, iso- and cyclopentane, are the major hydrocarbons under consideration. The leading HFCs being evaluated are HFC-245fa (CF3-CH0-CF9H) and HFC-365mfc (CF3-CH2-CF2-CH3).
The solubility of such blowing agents in many of the typical polyols and isocyanates used by the construction industry is limited. Additives have been used to improve the solubility of blowing agents in the past. For example, ethoxylated nonylphenol was added to many polyols in order to enhance CFC-11 (CCI3F) compatibility. A great many additives are being proposed today for use with hydrocarbons and HFCs.
This study examines the fundamental properties of various hydrohalocarbon and hydrocarbon blowing agents, and their relationship to solubility in polyurethane raw materials. The solubility of the various pentane isomers in many polyols and isocyanates used to produce insulation boardstock in a continuous lamination process is evaluated. The potential of many isocyanate modifications and polyol additives to improve blowing agent solubility is explored.
The effects of blowing agent solubility on the processing characteristics of foam properties are also examined. The data is used to examine the conventional theory regarding soluble systems - are such systems always necessary to get good processing? Many non-reactive or monofunctional additives that improve solubility are found to affect the structural, thermal or flammability performance of resulting foams. This paper presents data on potential methods to obtain robust processing and good perfonnance with the zero ODP blowing agents being considered by the rigid foam industry.
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