Items wrapped in shrinkable plastic film using
(see) Over Wrap, Sleeve Wrap or L type wrap
machine is then passed through a specially
designed Heat Tunnel of suitable size related to
wrapped items which shrinks the plastic film
to conform to the shape of the item.

Basic Description:

Shrinkwrap , 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.

Shrinkwrap is commonly used as an overwrap 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. It is also used to cover boats after manufacture and for winter storage.


Composition

The most commonly used shrink wrap is polyethylene. It is available in a variety of thicknesses, clarities, shrink ratios, etc. Other shrink films include PVC and several other compositions.

Coextrusions and laminations are available for specific mechanical and barrier properties for shrink wrapping food.

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.

Shrinkwrap 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.

Shrinkwrap 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. Some shrinkwraps are supplied in pre-formed plastic bags with one end open: the product is placed in the bag, sealed, and sent for heat sealing. Some food producers flush the bagged food item with gas or use vacuum prior to sealing and shrinking.