Shrink Wrapping

Shrink Wrap - The Material

ShrinkWrapping - The Process

Proper Materials

Proper Application Technique

Proper Training and Experience

Shrink Wrap Applications

Click on image to view shrink wrapping process.

Shrink Wrap - The Material

Shrink wrap is a low density polyethylene (LDPE) film made from a fractional low melt resin and other additives of ultra violet (UVI), ethyl vinyl acetate (EVA), color concentrates, etc.. The type of resins used and the extrusion process employed (blown film vs. cast film) in the manufacture of the film determine the quality of the shrink film. Other variables present in shrink films are:

anti-static agents which can be introduced to minimize static elecricity in polyethylene film,
balanced shrinkage characteristic which ensures that the shrinkage in one principal direction is not more than one and one-half (1 1/2) the shrinkage in the other principal direction. This characteristic prevents the film from "puckering" when heated and cooled.
Anti-Block Additive can be added to polyethylene in minute quantities to reduce the tendency of a layer of film to stick to another layer of film or other surfaces.

Other variables found in polyethylene shrink films are impact strength (the ability to withstand shock loading), initial tear resistance (the grams per mil thickness required to start a tear) and heat sealability (the quality of a heat-sealed seam of two layers of film). Top of Page

Shrink Wrapping - The Process

The proper protection of an object involves:

the selection of the proper materials to be used,
the selection of the proper application technique
the capabilitity of the person(s) performing the shrink wrapping process.

All three elements are equally important and deficiency in one cannot be offset by the others. Top of Page

Proper Materials - The old adage, "you get what you pay for", never held more true than when selecting shrink wrap materials. It is extremely difficult to distinquish the quality of shrink film by visual observation. The amount of UVI (ultra-violet inhibitors), EVA (ethyl vinyl acetate), anti-block additive, anti-static agents, biaxial orientation, break strength and elongation in film cannot be visually observed. A common misconception is that a thicker film (higher mils) is a better film. Mr. ShrinkWrap Protective Services' film is a specially formulated resin blend that provides superior strength and longevity to competitive films of greater millage.
Other materials used in the shrink wrapping process are:

Strapping and Buckles - Comes in 1/2" and 3/4" widths. Used in combination for perimeter straps, belly bands, and support straps. 1/2" strapping has 400 lb. tensile strength and is used on smaller objects. 3/4" strapping has 1100 lb. tensile strentgh and is used on larger items.

Shrink Film Tape - 2", 4", 6" Blue, White and Clear heat srink tape is a polyethylene film with a rubber adhesive applied to the under side. The tape is used for padding sharp edges, patching holes, reinforcing seams and fused pleats, and applying such accessories as screen vents and access doors.

Preservation Tape - 2", 3", 4", 6" Blue, White and Clear preservation tape is specially formulated shrink film tape used on items where the adhesive residue left when tape is removed is not desired. This tape is most widely know as "hull tape" since it is used to tape shrink film to fiberglass hulls.

Screen Vents - Plastic vents measuring 6" x 4.5" which allows a free flow of air to circulate through the shrink wrapped item preventing moisture and mildew build up. Vents are applied to the film cover after the shrinking of the film by taping the vent in place or by using the vents with self-adhesive backing.

Poly Foam Vents - A second means of providing ventilation within a shrink wrapped item. These are 24" x 3" x 2" and are only used on objects that have been wrapped with a perimeter strap as they fit between the object and the perimeter strap.

Poly Foam Padding - Comes in 6" and 48" widths. It is used to pad any sharp objects that might come in contact with the shrink film. It also creates a "lock down" point because the film will fuse to the foam when heat is applied.

Nylon Zipper Doors - Comes in 36" and 48" widths. Allows for the entry into a shrink wrapped item for inspection, repair or simply to do work on without having to cut the cover. Top of Page

Proper Application Technique - There are three (3) basic methods of shrink wrapping an object. The method used is determined by its size and shape; whether it is a shipping or storage cover; under what conditions it will be shipped or stored and the length of storage or transportation.

Perimeter Strapping - This method uses the 1/2" or 3/4" poly woven cord strapping and buckles to create the "framework" for the shrink film to be attached to the item. This method is most widely seen in protecting boats during winter storage where the strapping is secured around the perimeter of the hull. A variation of the perimater strapping is using existing "framework" such as scaffolding or pipes to secure the shrink film. It is important to remember that the shrink film will not adhere to the object being protected; it will only fuse to itself.

Total Encapsulation - This method is usually employed on smaller objects but can be done on large objects that can be lifted to permit the shrink film to be placed under it. This method offers the greaest protection since the entire object is sealed in the shrink film.

Tape Adhesion - This method utilizes either shrink film tape or preservation tape to adhere the shrink film to the object and then applying heat to tighten the film. This mehtod is used when only a portion of the object needs to be protected such as man-holes, car windows, tank openings, etc. Top of Page

Proper Training and Experience - This aspect of the shrink wrapping process is crucial to a successful and safe shrinkwrapping job. The person(s) doing the shrink wrapping must be properly trained in the use of the heat gun and aware of the dangers involved in using propane fuel. The work area should be examined for safety hazards such as flammable materials. The item being shrinkwrapped should be inspected for flammable objects and proper protection given those objects. It should be remembered that the average shrink film will have a "shrinking temperature range" of about 250 to 350 degrees F. The shrink film will melt at about 350 degrees F and will burn at 650 degrees F. The average heat gun has an output of about 125,000 BTU/Hr and a heat output/velocity of 1200 degrees F./2800 feet per minute at a range six (6) inches from the nozzle, and 750 degrees F./1700 feet per minute at a range twelve (12) inches from the nozzle. All heat guns sold by Mr. ShrinkWrap Protective Services, Inc. operate by propane gas. Propane has three safety hazards associated with its use: flammable, it's under pressure, and it can freeze. Top of Page

Click an image to view Before and After photos