QUALITY CONTROL OF CLOSURES
A number of quality control checks are required for the manufacture and release of closures. These checks include:
After the material has been mixed
- Specific gravity, which is the ratio of the weight of the molded piece to the weight of an equal volume of water
- Color, which can be checked against a color chart
- Dispersion of a vulcanized sample in relation to particle size
- Examination of the ash after burning in comparison to a reference sample
- Hardness, which can be measured in Shore Units or an equivalent standard
- Rheology of the compound, by conducting an examination of solids under conditions in which they respond with plastic flow
rather than deforming elastically in response to an applied force. This is an assessment of the force necessary to rotate
the material by 1°.
An important distinction is that different materials—types of rubber and formulations—have different profile and respond in
different ways.
Post-compression and molding
The material is checked for rubber thickness and evenness.
Washing process
- During the loading of stoppers into a washer, the quality of the water should be checked for bioburden and endotoxin using
compendial methods.
- The loading of the washer should take place in a controlled environment, usually a cleanroom, with staff appropriately gowned.
Unusually for a pharmaceutical process and in keeping with cleanrooms used in the electronics industry, the cleanroom may
be fitted with deionization equipment in order to avoid fibers being attracted to the rubber.
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