A closure for a polymeric container configured to be filled with a commodity by a hot-fill process. The closure includes an outer metallic ring and a flexible membrane. The flexible membrane is removably sealed across the ring and is configured to be drawn from an outward, pre-fill configuration to an inward, post-fill configuration in response to a vacuum created within the container during the hot-fill process. In the inward, post-fill configuration the flexible membrane is concave relate to an outer side of the closure.

Disclosed are a sealing structure for a packaging box, a production process for the sealing structure, and a packaging box. The sealing structure includes: a pull piece, an inner membrane, and a plug sheet, the pull piece covers an outer side of an opening in a packaging box, the inner membrane covers an inner side of the opening, an area of the pull piece and an area of the inner membrane are is both greater than that of the opening, and; the plug sheet matches a shape of the opening and corresponds to a position of the opening; the pull piece enables the inner membrane to be broken at the opening under an action of an external force, so as to open the opening; and the plug sheet is able to be embedded in the opening under an action of an external force, so as to close the opening.

A closure for a polymeric container configured to be filled with a commodity by a hot-fill process. The closure includes an outer metallic ring and a flexible membrane. The flexible membrane is removably sealed across the ring and is configured to be drawn from an outward, pre-fill configuration to an inward, post-fill configuration in response to a vacuum created within the container during the hot-fill process. In the inward, post-fill configuration the flexible membrane is concave relate to an outer side of the closure.