Shrink wrap

Polymer used to bundle boxes on a pallet for transport

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This article is about heat shrink film. For tubing, see Heat-shrink tubing

Grocery vegetables wrapped with a plastic shrink film. Shrink wrapped ball of twine

Shrink wrap, also shrink film, is a material made up of polymer plastic film. When heat is applied, it shrinks tightly over whatever it is covering.[1][2][3] Heat can be applied with a handheld heat gun (electric or gas), or the product and film can pass through a heat tunnel on a conveyor.

Composition

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The most commonly used shrink wrap is polyolefin.[citation needed] It is available in a variety of thicknesses, clarities, strengths and shrink ratios. The two primary films can be either crosslinked, or non crosslinked. Other shrink films include PVC, Polyethylene, Polypropylene, and several other compositions.

Coextrusions and laminations are available for specific mechanical and barrier properties for shrink wrapping food. For example, five layers might be configuration as EP/EVA/copolyester/EVA/EP, where EP is ethylene-propylene and EVA is ethylene-vinyl acetate copolymer.[1]

PVC is the most used shrink wrap, due to its light weight, and inexpensive capabilities. PVC is durable, and can be used for many different purposes.[dubious ' discuss] However, it should be used in a well-ventilated area, as it can give off a strong, harmful odor. PVC has been banned in many countries, due to the harmful products created by its decomposition. PVC has some negative qualities including, it is not good for bundling, leaves carbon deposits, and has a low shrink force.[citation needed]

Polyolefin or POF shrink wrap is a premium shrink wrap, as it is extremely durable and versatile. POF is puncture resistant, and has a strong seal strength, which allows it to be used for irregularly shaped items. POF is available in 35, 45, 60, 75, and 100, 1 mil gauges. POF shrink wrap is made from 100% recyclable materials, and is FDA approved. It has great clarity, and a glossy self-appearance, as appearance is critical. POF is great for bundling multiple items together, and has the ability to shrink completely and quickly.

PE, a polyolefin, is used in several forms of flexible protective packaging. There are 3 different forms PE can take place in. These include Low-Density Polyethylene (LDPE), Linear Low-Density Polyethylene (LLDPE), and High-Density Polyethylene (HDPE). For shrink wrapping LDPE would be the best choice, as it has a higher strength, and more durability for heavier items. These wraps can also have graphic images printed on them, and LDPE provides the greatest quality. PE gauges can go all the way up to , allowing for a great range of gauges. The disadvantage for PE is that it does not have a great shrink rate, and has lower clarity than other wraps.

Manufacture

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A machine designed to continuously wrap up to 35 packets per minute

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.

Prior to orientation, the molecules of a sheet or tube are randomly intertwined like a bowl of spaghetti. The molecules are coiled and twisted and have no particular alignment. However, when a draw force is imposed, the amorphous regions of the chains are straightened and aligned to the direction of orientation. By applying proper cooling, the molecules will be frozen in this state until sufficient heat energy is applied to allow the chains to shrink back. One can visualize this phenomenon by stretching a rubber band and dipping it into liquid nitrogen so as to freeze in the stretched state. The band will remain in this state as long as it is kept at sufficiently cold temperatures. However, when enough heat energy is applied, the rubber band will shrink back to its original relaxed state.

Orientation on a commercial scale can be achieved using either of two processes: a tenterframe or a bubble process. Tenterframe technology is used to produce a variety of 'heat-set' products, with biaxially oriented polypropylene (BOPP) being the most common (heat-setting is a process whereby a film is reheated in a constrained state such that the shrink properties are destroyed).

The second commercial process is the bubble process, sometimes referred to as the tubular process. In this process, a primary tube is produced by either blowing or casting the tube onto an external or internal mandrel, respectively. It is common to use water to help cool the primary tube at this point. After the primary tube has been cooled, it is then reheated and inflated into a second bubble using air much like a balloon is blown. Upon inflation, the tube is oriented in both directions simultaneously.

The family of shrink films has broadened over the years with many multi-layer constructions being sold today. Shrink film attributes include shrink, sealability, optics, toughness, and slip. With regard to shrink properties, there are onset temperature, free shrink, shrink force, shrink temperature range, memory, and overall package appearance.

Use

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Shrink wrapped helicopters for transport Shrink film wrap being applied on a soft drink packing line Shrink wrapped pack of bottles with ends (bulls eyes) as handles

Shrink wrap is applied over or around the intended item, often by automated equipment. It is then heated by a heat gun or sent through a shrink tunnel or oven for shrinking.

Shrink wrap can be supplied in several forms. Flat rollstock can be wrapped around a product, often with heat sealing to tack the film together. Centerfolded film is supplied on a roll with the plastic pre-folded in half, product is placed in the center portion, the remaining three edges are sealed to form a bag, and the package then heated which causes the bag to shrink and conform to the product. Pre-formed plastic shrink bags have one end open, the product is placed in the bag, sealed, and sent for heat shrinking.

Shrink wrap can be used to wrap buildings. It can wrap roofs after hurricanes, earthquakes, tornadoes and other disasters. Shrink wrap can be used for environmental containments to facilitate safe removal of asbestos, lead and other hazards.

Shrink wrap is sometimes used to wrap up books, especially adult-oriented ones and premium comics and manga, mainly to preserve their mint condition, as casual previewing prior to purchase wears or damages stock, rendering it unsaleable.

Vegetables such as cucumbers can be individually shrink wrapped to extend the shelf life.[4]

Software on carriers such as CDs or DVDs are often sold in boxes that are packaged in shrink wrap. The licenses of such software are typically put inside the boxes, making it impossible to read them before purchasing. This has raised questions about the validity of such shrink wrap licenses.

Shrink wrap is commonly used as an overwrap on many types of packaging, including cartons, boxes, beverage cans and pallet loads. Foam cushioning can be held securely in shrink film, eliminating use of a traditional corrugated box.[5] A variety of products may be enclosed in shrink wrap to stabilize the products, unitize them, keep them clean, or add tamper resistance. It can be the primary covering for some foods such as cheese, meats, vegetables and plants. Heat-shrink tubing is used to seal electric wiring.

Shrink bands are applied over parts of packages for tamper resistance or labels. It can be used as a Tamper-evident band.

It can also combine two packages or parts into a Multi-pack.

Shrink wrap is also commonly used within more industrial applications using a heavier weight shrink film. The principles remain the same with a heat shrinking process using a hand held heat gun. The following shrink wrap applications are becoming more widely used and accepted:

• Industrial shrink wrap containment of large plant equipment/components,
• Scaffold wrap containment of buildings/bridges,
• Building temporary shrink wrap structures for storage or other business operational uses,
• Marine shrink wrapping of boats and other vehicles,
• Shrink wrapping of palletized freight

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• Disaster contingency and relief projects such as damaged buildings/roofs.

See also

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References

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Further reading

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• Soroka, W, "Fundamentals of Packaging Technology", IoPP, , ISBN 1--25-4
• Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, , ISBN 978-0-470--6

ASTM standards

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• D882 Standard Test Method for Tensile Properties of Thin Plastic Sheeting
• D883 Standard Terminology Relating to Plastics
• D Standard Test Method for Linear Dimensional Changes of Nonrigid Thermoplastic Sheeting or Film at Elevated Temperature
• D Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting
• D Standard Test Method for Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method
• D Standard Test Method for Unrestrained Linear Thermal Shrinkage of Plastic Film and Sheeting
• D Standard Test Method for Shrink Tension and Orientation Release Stress of Plastic Film and Thin Sheeting

Patent classifications

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• B65D71/10 Wrappers shrunk by heat or under tension, e.g. stretch films or films tensioned by compressed articles and provided with inserts [1]
• B65B61/02 Auxiliary devices, not otherwise provided for, for operating on sheets, blanks, webs, binding material, containers or packages for perforating, scoring, slitting, or applying code or date marks on material prior to packaging [2]

YH Package Product Page

PVC shrink film centre folded film, Economical film for many applications with various shrink ratios

The three main wraps used in shrink packaging material for protecting and securing products for the retail and shipping environments are polyvinyl chloride (PVC), polyethylene (PE), and polyolefin (POF). Each have different capabilities and characteristics that make them suitable for specific applications.

 

What are the main differences between these types of shrink wrap? Which is the best choice for your packaging needs? Read on to find out!

 

Each of these three wraps can be co-extruded into multilayer wraps with different additives offering specific barrier properties required for shelf-life or appearance. Shrink wraps can be formed into flattened rollstock, bags, overwrap, banding and tubing, and add a form of tamper-resistant protection to packaged goods. If you aren't sure that you are using the ideal wrap for your application, here's a breakdown of the three:  

PVC SHRINK WRAP

Once the most commonly-used shrink packaging material in the world due to its light-weight and inexpensive multi-purpose capabilities, PVC Shrink wrap has since taken a backseat to PE and POF for many reasons. Most specifically due to the dangers in health during creation and incineration, and sustainability.

 

In its rigid form, PVC is durable and is used in many applications, including construction projects and houseware products. In terms of packaging, PVC is seen in rigid applications including blister and clamshell packaging, & flexible applications including shrink wrap, bagging. Polyvinyl chloride is a combination of three elements, carbon, hydrogen, and chlorine. 

 

It is recommended for use in well-ventilated facilities due to the strong, harmful odors that are released when heated. Due to its chemical composition and these harmful byproducts released during its creation, and decomposition for that matter,

Fast Facts About PVC Shrink Wrap:

• Once the most commonly used shrink wrapping material in the world
• Temperamental with hot and cold temperature changes, causing brittleness when too cold and wrinkling when too warm
• Higher resistance to propagation of tear, Polyolefin- higher resistance to puncture
• If you utilize a PVC wrap, its important to ensure the highest possible standards for use and disposal are used across your supply chain
• Applications for PVC Shrink wrap include: packaging of CD's/DVD's, boxes for gaming & software, and other non-edible items
• Not good for bundling multiple items together due to its more brittle nature after shrinking
• Releases harmful odors during sealing and heating, caution and proper ventilation are a must

Polyolefin shrink is an extremely durable and versatile 'premium' shrink wrap. It has taken the place of PVC mentioned above in many applications, and is also an FDA-approved food-safe material. Polyolefin materials are available with different characteristics, including cross-linked wrap that provides high-tensile strength and incredible clarity for high-speed packaging applications. Cross-linked wrap also prevents buildup on sealing components of your packaging machinery.

Fast Facts About POF Shrink Wrap

• Premium quality shrink wrap, AKA high-clarity, decorative shrink wrap. 
• Made of 100% recyclable materials
• Excellent clarity and glossy shelf appearance; great for consumer products where appearance is critical (toys, games, candies, books, foods, most retail items)
• Ability to shrink quickly and completely (shrinks when heated resulting in a finished good as soon as it comes out of the shrink tunnel)
• Durable, versatile, low cost
• Excellent for bundling multiple items together, like tissue boxes for example.
• Cross-linked POF is great for high-speed applications, providing added strength without compromising clarity and prevents build-up on sealing components
• Polyolefin is more expensive, but more durable- not as effected by temperature changes
• FDA approved for food contact
• Excellent tensile-strength and propagation-to-tear
• Pre-perforated POF is available and allows for even shrink surface, no air pockets
• the 4 types we stock are below

DARNEL P3LS

Excellent clarity and high speed * performance  100%  Exceptional tensile strength and tear resistance

Very strong static seals

Available in 12.5 - 25 micron

 DARNEL P5HS 

A 5 layer, multi-purpose film with a high yield

Gives excellent results on manual and automatic high speed machines                             High shrinkage performance, good optics and excellent hot slip properties

Available in 9 - 25 micron

   DARNEL P10

 Excellent clarity and high speed performance  Exceptional tensile strength and tear resistance

Very strong static seals

Available in 18 - 38 micron

DARNEL P5AF

 Excellent clarity and high speed performance  Exceptional tensile strength and tear resistance

Very strong static seals

• Available in 13 - 19 micron

DARNEL SAO / SMS for fruit meat and vegetables

Suitable for fresh and raw goods, meats, fruit, vegetables and bakery produce

Keeps food fresh and prevents flavour and odour transfer from food

Conforms to any product shape                 

Available with or without perforations

Standard or double-layer

Final Thoughts On Shrink Wrap And Stretch Wrap

 

No matter what the application, knowing your options can help save you money in the long run. It's always best to connect with a supplier that can answer any of your questions that you haven't found clear answers to. They can also help you with custom packaging solutions that match your needs for efficiency, protection, and visual presentation.

 

If you are using shrink wrap to package your products, we've created a Shrink wrap Cheat Sheet to help you know whats best for your product

Sometimes paying a little extra for better customer service is worth a few extra euro. In the end, you will want to find a balance between quality customer service and quality products. By utilizing all the information above, you will be armed with the knowlede needed to make the best choice in regards to your wrap and the supplier you buy from.

call me at or if you need any more information for shrink and machinery you require

 

 

If you want to learn more, please visit our website Wholesale Shrink Wrap Film.