| 摘要 |
A process of reticulating polymeric cellular materials having cell membranes comprises heat treating the cellular material for a sufficiently short time such that the bulk of the cellular material is not damaged and until at <PICT:1063462/C3/1> least some of the cell membranes are heat stabilized. The process is preferably carried out with cellular polyurethane material by providing a combustible composition of an oxidizing material and an oxidizable material with the cellular material and igniting the combustible composition. In Fig. 3 a sample of cellular polyurethane material having the same dimensions as the inside of the chamber 22 formed by the container 21 and cover 20 is positioned in the chamber 22. Air is removed from the chamber using a vacuum pump attached to tube 23 with tube 24 closed. A mixture of oxygen and natural gas is then introduced through tube 23 which is then closed. A spark is initiated between the spark gap terminals 25 and 26 by closing the switch S and the gaseous mixture is ignited. After combustion, gaseous combustion products are removed by flushing the chamber 22 with air with the valve tubes 23 and 24 open. A similar process may be carried out using a non-rigid container such as a polyethylene bag. Other suitable cellular materials may be derived from ethylenically unsaturated monomers and may be for example polystyrene, acrylics, polyolefines, e.g. polyethylene and polypropylene, vinyl resins, e.g. plasticized or unplasticized polyvinyl chloride and its copolymers and terpolymers, cellulose derived polymers and natural and synthetic rubber. Suitable oxidizable materials are hydrogen lower alkanes, alkenes or alkynes such as methane, ethane, propane, pentane, octane, decane ethylene, propylene acetylene and methyl acetylene, ammonia, hydrazine, hydrogen sulphide and gasoline. The preferred oxidizing material is oxygen but air, ozone and perchlorates may be used. An alternative procedure comprises exposing the cellular material to heat generated from a pulse of electromagnetic radiation by mounting the sample in the centre of a helical photoflash lamp. In this process the cellular material may be coated with a light absorptive material which does not evaporate upon heating, e.g. carbon, graphite, metal sulphides and metal oxides such as iron oxide, lead oxide and titanium oxide. A further alternative procedure is to provide a cellular material in a confined space with a gas such as air and to rapidly increase and decrease the pressure in the confined space, thus heating and cooling the gaseous material and transiently heating the cellular material whereby it is reticulated. |
