A clamshell is a one-piece container consisting of two halves joined by a hinge area which allows the structure to come together to close. Clamshells can be made to be reusable and reclosable or can be sealed securely.

History

Containers acting similar to clamshells have been widely used for many years, constructed from a diversity of materials. Patent Classification B65D43/162 covers “Non-removable lids or covers hinged for upward or downward movement the container, the lid and the hinge being made of one piece". It lists over ten thousand patents in the last hundred years. Foam plastic clamshells have been used in fast food restaurants for burgers; paperboard clamshells are currently being used similarly. Clear plastic clamshell containers were used for strawberries by Driscoll’s, a California berry grower, in the 1990s to pack its berries for retail sale.

Construction

Clamshell containers can be made of a variety of materials. Plastics such as

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It i ...

polyester Polyester is a category of polymers that contain one or two ester linkages in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include some natura ...

, PVC, foam sheets, etc. The material can be made by

thermoforming Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product. The sheet, or "film" when referring to thinner gauges and cert ...

or can be injection molded into the desired shapes. A single piece of material is used for the top and bottom with a " living hinge" that is integral to the material, rather than added separately.

Folding carton The folding carton created the packaging industry as it is known today, beginning in the late 19th century. The process involves folding carton made of paperboard that is printed, laminated, cut, then folded and glued. The cartons are shipped f ...

s made of

paperboard Paperboard is a thick paper-based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker (usually over 0.30 mm, 0.012 in, or 12 Inch#Equivalents, points) than paper and has certain superior ...

molded pulp Molded pulp or molded fiber (also spelled as moulded pulp or moulded fibre) is a packaging material, that is typically made from recycled paperboard and/or newsprint. It is used for protective packaging or for food service trays and beverag ...

can also be of a clamshell shape. It can also be made of cellulose fiber such as sugarcane-

bagasse Bagasse ( ) is the dry pulpy fibrous material that remains after crushing sugarcane or sorghum stalks to extract their juice. It is used as a biofuel for the production of heat, energy, and electricity, and in the manufacture of pulp and building ...

, wheatstraw, wood pulp, etc.

Closing

Clamshells can use a variety of means of closing or sealing. Some have self-locking tabs, snaps, or have a friction fit. Others use

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantage ...

pressure-sensitive tape Pressure-sensitive tape or pressure-sensitive adhesive tape (PSA tape) is an adhesive tape that sticks when pressure is applied without the need for a solvent (such as water) or heat for activation. It is also known in various countries as self ...

label A label (as distinct from signage) is a piece of paper, plastic film, cloth, metal, or other material affixed to a container or product. Labels are most often affixed to packaging and containers using an adhesive, or sewing when affix ...

s, staples, or are heat-sealed.

Opening

Many clamshell containers are easy to open, and reuse, by consumers. When plastic clamshell containers are securely heat sealed, they are tamper resistant and deter package pilferage. These security packages are intentionally difficult to open, sometimes requiring customers to use scissors or a knife. Difficulty opening such packaging can be frustrating to the point of wrap rage. Some people injure themselves trying to open security packaging which in the United Kingdom has been cited as the most frustrating to open.

Notes

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