Examples of blowing agents include aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane and n-hexane; cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; and halogenated hydrocarbons such as methyl chloride, ethyl chloride, dichlorodifluoromethane, chlorodifluoromethane and trichlorofluoromethane.