Closure (container)

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.

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.

Some screw tops have multiple pieces. For example, a mason jar often has a lid with a built in rubbery seal and a separate threaded ring or band.

Beverage bottles are frequently closed with crown beverage caps. These are shallow metal caps that are crimped into locking position around the head of the bottle.

Some closures snap on. For opening, the top is designed to pry off or, break off, or have a built in dispenser.

Some containers have a loose lid for a closure. Laboratory glassware often has ground glass joints that allow the pieces to be fitted together easily.

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Wikipedia