Examples of physical foaming agents include a hydrocarbon, such as pentane, butane or hexane; a halogenated hydrocarbon, such as methyl chloride or methylene chloride; a gas, such as nitrogen gas or air; and a fluoridated hydrocarbon, such as trichlorofluoromethane, dichlorodifluoromethane, trichlorotrifluoroethane, chlorodifluoroethane or a hydrofluoro carbon.