| 摘要 |
A composition comprising a plastic material such as natural or synthetic rubber such as neoprene, polymerized butadiene or polyvinyl polymerization products, and a lubricating fatty or waxy substance such as solid paraffin, paraffin oil or ozokerite, the mixture having the property of continuously exuding the fatty or waxy substance from its surface, is used for the manufacture of the fluid-tight piston packing device comprising portions having different mechanical properties which is described in Group XXVI.
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