Screw cap beverage bottle

The photographs show transverse and longitudinal sections of gas-tight screw caps with MCA thread (Metal Closure Aluminium). They are made of aluminium with a sealing compound of thermoplastic elastomer (TPE plastic).
The sealing compound was checked geometrically for quality monitoring, which was only possible in metallographic sections. The challenge here was the deformation-free sampling and embedding. We vapour-deposited the screw cap to increase the contrast.