Abstract
Rigid foams blown with hydrocarbons have shown a great progress since this technology was implemented in 1992 in Europe, and culminated, last year, in the introduction of blends of hydrocarbons and more particularly cyclopentane/isobutane. Also recently, other blends have found favor where the more complicated handling of butane may present some difficulties.
In the hydrocarbon family, cyclopentane is the best option in terms of gas k-factor, but its high boiling point requires higher density and shot weights in cabinets to guarantee long term dimensional stability. The best cost option is provided by the iso-/n-pentane blend. However, the foams produced show inferior k-factor, although final energy consumption is not affected to the same degree.
In general, the addition of another co-blowing hydrocarbon such as isobutane, isopentane or c-pentane negatively affects the insulation performance of the foam, but recent polyurethane system developments have allowed the retention of the same k-factor values as those of pure cyclopentane blown foams.
This paper aims to compare the different hydrocarbon blowing agent alternatives introduced during the past period and includes theoretical cell gas modeling, creep performance and compressive strength ageing tests. These methods have been used to evaluate and predict, during the foam development phase, the short and long term dimensional stability of the foam. An attempt will be made to understand if the combination of all of them is necessary for getting reliable information.
Results from cabinets foamed with these cyclopentane based hydrocarbon blends have confirmed the initial findings and are discussed.
It is a further objective of this paper to give the OEMs the data that they require to select the optimum technology to answer their needs in terms of cost, processing performance and insulation value.