Rubber types overseals

Primary pack Type 1 clear glass vial (10 m L) Rubber stopper Aluminium overseal... 

Special mention should be made of closures for IV solutions. The use of any screw closure with an inner rubber wad or plug always presents an unscrewing risk due to a watch spring effect. In addition, threading may hide a contamination due to residual cooling water. An overseal-type closure, similar to that employed for vials, appears to offer advantages (DIN Standard). 

The top seal (overseal) may be a small stopper, a modification of a stopper, a disc or a combination-type system. Each normally requires rubber under compression held in position by an aluminium crimped, rolled-on, etc. overseal. The second sealing surface may be glass or plastic. In the case of glass cartridge tubes, these are invariably produced from the tubular or cane glass process, hence suffer from imperfections associated with this shaping process. Plastic cartridges have never proved popular but are available. 

Double rotor chainmill-type crushers or double row cage mills are preferred. The discharge assembly of the mill should not be restricted and should be constructed of flexible rubber (conveyor belting) panels that can be flexed from the outside by an operator using a hammer. A flared-type discharge assembly for the crushers.is recommended to help avoid the accumulation of solids. The crushed oversize should be recycled to the oversize screen on a closed-loop basis to ensure that only the fine-material fraction (undersize) from the screens is returned... 

If the manner of packing is denser in some locations than others, the denser parts may be regarded as the previously mentioned flocculates. The other extreme is the presence of unmixed rubber, which is an oversized rubber domain. Both types of the inhomogeneity are very difficult to break up they are similar to the formation of lumps in a flour-water mixture. The presence of unmixed rubber is reported to occur sometimes in the mixing of EPDM [46]. 

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