Shrink wrap packaging involves the use of thermoplastic or thermosetting films that shrink when heat is applied to them.
The film is first wrapped/sealed around the product to be packaged -- forming a loose bag or envelope. Heat is applied and the film shrinks tightly to the contour of the product.
Usually the shrink wrap process uses centerfolded shrink film - film that has been folded in half and wound into a roll. The package is formed by sliding the product to be wrapped between the center folds of shrink film.
Using either an I-Bar sealer or a L-Sealer the package is then sealed on three sides to form the loose envelope of film around the product. In a matter of seconds, the film is sealed and cut simultaneously.
With the I-Bar type sealer, one seal is made at a time. The package is then turned to seal and cut the open side of the film envelope/bag just made.
The L-Sealer is faster. It makes two simultaneous seals at right angles to each other and it is not necessary to turn the package.
The film envelope/bag is then shrunk around the product using a heat gun of shrink tunnel to shrink . This requires several seconds depending on the package size.