Pentane Blown Polyurethane Foams

HCFCs (hydrochlorofluorocarbons) were developed as a CFC (chlorofluorocarbon) replacement but considered only as a short-term solution since their ODP (ozone depletion potential) is not zero. With HFCs (hydrofluorocarbons), which are considered as the next generation of blowing agents, a basic problem arises: in order to be non-flammable and to have a low thermal conductivity the fluorine content of the molecule must be high. This means, however, high production costs and an increased GWP (greenhouse warming potential). For this reason a consequent change to halogen-free hydrocarbons has taken place in Europe. Pentane isomers were chosen as the only suitable candidates due to their boiling points. In flexible integral skin foam n-pentane was introduced already 4–5 years ago. Density distribution and mechanical foam properties of Rll and n-pentane blown integral skin foams are nearly identical. Rigid foams, where thermal conductivity and low permeation of the cell gas from the foam are important properties, must be considered more individually. In sandwich panels for the construction industry a higher thermal conductivity can, if necessary, be compensated for by increasing the thickness of the part. In this area less expensive n-pentane and isopentane are used. In the appliance field an increase in wall thickness is hardly possible. Here cyclopentane is used, whose thermal conductivity is similar to that of the best HFCs. Permeation of all pentane isomers from PUR-foam is as low as that of R11, resulting in a similar ageing behavior. Also similar are thermal conductivity at low temperature and mechanical properties of R11 and pentane blown foams. The increased flammability of pentane foams can be overcome by adding additional flame retardant and by proper adaption of the foam formulation. Safe procedures have been developed and are offered for the processing of flammable blowing agents. In Europe, cyclopentane has been used in refrigerators for the past 2 years and n-pentane has been used in flexible integral skin foams for 4–5 years without any major problems.