| 摘要 |
<p>A porous membrane is made by stretching a rubber or plastics material, perforating the material and then reducing the material to decrease the pore size. The material may be a heat shrinkable plastics material which has already been stretched in the course of manufacture. The material is preferably tubular in form and a support, for example a helical spring, may be disposed therein. The porous membrane may be used as a flow control element which has particular application in a method of diffusing a fluid into a surrounding medium, for example air into sewage.</p> |
