Three layer co-extruded liner - PP-PP-PP

A three layer co-extruded liner: two solid polypropylene surfaces cover a central layer of foamed polypropylene with closed cells. This structure is a single polymeric unit which cannot delaminate.
The foamed center core provides the resiliency needed for sealing and the solid facings prevent evaporation and product penetration.

The liner usually inserted into aluminium, plastic or metal caps and therefore become part of them. When the bottle or jar is opened, the liner remains in the cap.