Until the 90's, CFC's were extensively used in the aerosol and foam blowing industries, until the banning of their use led to their replacement by hydrocarbons in these applications. In aerosols, the propellant needs to be a liquid with a vapour pressure slightly higher than atmospheric and with a boiling point lower than room temperature. Hydrocarbons such as propane, and butanes may be mixed together to achieve specific vapour pressures and boiling points making them ideal in these circumstances. The only downside is their flammability which is not a significant issue given the small volumes in the can.
Polyurethane foams are manufactured by adding blowing agents such as the mixture iso-Butane/DME (Dimethilether) as well as pure iso-butane, n-butane, propylene and pentanes to the liquid reaction mixture. All these products are excellent agents since they are volatile and have an ideal boiling point and vapour pressure. Since the polymerization process is exothermic the blowing agent volatizes into a gas during the reaction process, which fills and expands the cells created during the mixing process, thus creating a solid foam.