Closure (bottle)

Closures are devices and techniques used to close or seal a bottle, jug, jar, tube, , etc. Closures can be a cap, cover, lid, plug, etc.

Other types of containers such as boxes and drums may also have closures but are not discussed in this article.

Many containers and packages require a means of closing. It can be a separate device or seal or sometimes an integral latch or lock. Depending on the contents and container, closures have several functions:

Many types of packaging with their closures are regulated for strength, safety, security, communication, recycling, and environmental requirements.

Closures need a means of attaching to the container with sufficient security. Threads, lugs, hinges, locks, adhesives, etc. are used.

Many closures need to have the ability to adjust to slight manufacturing variation in the container and the closure structure. Some closures are made of flexible material such as cork, rubber, or plastic foam. Often an o-ring or a closure liner (gasket made of pulp or foam cap liner) is used. Linerless closures often use a deformable plastic rim or structure to maintain the seal.

Secondary seals are common with sensitive products that may deteriorate or where extra security is needed. Foil or plastic innerseals are used on some bottles, Heat sealed lidding films are used on some tubs. External shrink bands, labels, and tapes are sometimes used outside the primary closure structure. Additionally, many closures feature ventilation to prevent bloating, collapse or explosion due to unequalized pressure during processing or storage. Venting technologies utilize common materials such as PTFE, PP, etc. These elements are preferred due to their ability to withstand temperatures of 260°C and water intrusion pressure levels of 770 mbar.

A screw closure is a mechanical device which is screwed on and off of a threaded "finish" on a container. Either continuous threads (C-T) or lugs are used. Metal caps can be either preformed or in some instances, rolled on after application. Plastic caps may use several types of molded polymer.

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