microcellular foams can be obtained in a collapsed form or in a fully or partially inflated form for many polymer solvent systems microcellular foams tend to collapse after exiting the spinning orifice as the solvent vapor condenses inside the cells and or diffuses out of the cells to obtain low density inflated foams inflating agents are usually added to the spin liquid suitable inflating agents that can be used include low boiling temperature partially halogenated hydrocarbons such as hydrochlorofluorocarbons and hydrofluorocarbons or fully halogenated hydrocarbons such as chlorofluorocarbons and perfluorocarbons hydrofluoroethers inert gases such as carbon dioxide and nitrogen low boiling temperature hydrocarbon solvents such as butane and isopentane and other low boiling temperature organic solvents and gases microcellular foam fibers are normally spun from a round cross section spin orifice however annular dies similar to the ones used for blown films can be used to make microcellular foam sheets in the description above and in the non limiting examples that follow the following test methods were employed to determine various reported characteristics and properties astm refers to the american society of testing materials and tappi refers to the technical association of the pulp and paper industry the denier of the strand is determined from the weight of a 15 cm sample length of strand under a predetermined load tenacity elongation and toughness of the.