Shrink wrap, also shrink wrap or shrink film, is a material made up of polymer plastic film.When heat is applied to this material it shrinks tightly over whatever it was covering.Shrink wrap is commonly used as an over wrap on many types of packaging : CDs, DVDs, cartons, books, beverage cans, large appliances, pallet loads, etc.It can be the primary covering for some foods such as cheese and meats.

Composition

The most commonly used shrink wrap is polyolefin. It is available in a variety of thicknesses, clarities, strengths and shrink ratios.The two primary films are either crosslinked, or non crosslinked. Other shrink films include PVC and several other compositions.

Manufacture

A shrink film can be made to shrink in one direction (unidirectional or mono-directional) or in both directions (bidirectional).Films are stretched when they are warm to orient the molecules from their initial random pattern.Cooling the film sets the film's characteristics until it is reheated: this causes it to shrink back toward its initial dimensions.

Use

Shrink wrap is applied over or around the intended item, often by automated equipment.It is then sent through a heat tunnel or oven for shrinking. Heat guns are also used for large items.Shrink wrap can be supplied in several forms. Flat rollstock can be wrapped around a product,sometimes with a form-fill-seal machine. Centerfold film is supplied on a roll but is two thicknesses with a fold along one edge:the product is placed in the center portion, the remaining three edges are sealed, and the package is sent for heat shrinking.