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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 twineShrink 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 minuteA 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 handlesShrink 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:
See also
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References
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Further reading
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Contact us to discuss your requirements of recycled petg. Our experienced sales team can help you identify the options that best suit your needs.
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ASTM standards
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Patent classifications
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What is shrink film? Shrink film is a packaging plastic, but why is it popular? The product that reaches the final consumer should have a great appearance to make them feel good and continue to buy. On the other hand, using suitable packaging will increase the lifespan and reduce costs in transportation and maintenance. One of the cheapest and easiest packing methods is nylon shrink wrap.
Shrink is a type of plastic packaging that is convenient to use. By using shrink roll and heat, you can organize the products. Due to its flexibility, remarkable durability, low price and other valuable advantages, many companies use it for packaging their products. Shrink film is a versatile polymer material that is used for final packaging. Heat is applied to the film by methods such as a heat tunnel, conveyor belt, electric or gas heat gun, and sometimes manually, etc., and the film tightens very quickly around the goods inside. This process creates a clear and durable barrier, protector and retainer around the products.
Until sufficient thermal energy is applied to the molecular chains and the film shrinks, shrink remains in its initial state. These films are available with different raw materials, thicknesses, transparency, strength and shrink ratios, which can help us implement special packaging and proper protection of the items. This diversity allows us to meet specific requirements regarding sealing, design, transparency, temperature, power and maintenance.
In the following, we will examine the seven features of these films that we should know before buying to make a suitable choice for different products.
This force (pressure) is usually measured in psi and is the force the film exerts on the product after shrinking. Understanding this force will be helpful if you are packing products that need to be tightly sealed and not damaged. Especially when adjusting the shrink machine, it is better to make the adjustment based on that.
In general, polyolefin films have more contraction force. Polyvinyl chloride (PVC) films have a low shrinkage force. However, newer polyolefin formulations offer a lower amount of shrinking force.
This specialized feature describes the orientation of the film molecules after cooling. There are two types of shrink film direction: preferentially and bi-axially. The film is placed bi-axially in the machine&#;s and the product&#;s directions equally. But films with preferential orientation shrink preferentially in any order.
In addition to changing the roll percentage using the preferred orientation film, you can reduce the roll amount and stay with a bi-axial film. Another related feature is Free shrink. This feature refers to the ability of a film to shrink before contact with the product. The high level of Free shrink allows us to have a better-looking package in complicated shapes and sizes.
This property tells us how likely the film is to be punctured and how tear-resistant it is when it is stuck. Most films with high puncture resistance have lower tear resistance and vice versa. Deciding which of these two features is essential depends on the product type. Be sure to store the shrink in a cool environment before use to prevent it from weakening before use.
This characteristic measures how much moisture will pass through the film. This feature should be considered to improve the useful life. This feature is more important for food products.
Films with this feature are used in the fresh and frozen food packaging industry to reduce moisture in the film. Water can cause fog (steam) that affects the appearance of the product under the film. Films with this feature are created by adding other materials to the film structure during production.
Films with this feature are used to prevent unpleasant odours from entering or exiting the package. Especially for food or packaging of goods that are kept in environments with different smells and chemicals, the importance of this feature increases. For example, food and protein materials are practically unusable if the film hasn&#;t this feature.
Three types of films are used for packaging, storage and transportation of products: polyvinyl chloride, polyolefin and polyethylene. Each of these materials has different capabilities and characteristics that make them suitable for specific applications. In addition, each can be simultaneously pressed into multiple layers with various additives to create distinct properties that increase durability or give a unique appearance.
Due to its lightweight, low price and multi-purpose capability, PVC has been one of the world&#;s most common primary materials for shrink packaging. But it has given way to polyethylene (PE) and polyolefin (POF) for various reasons, including the health hazards of creating and burning, as well as its level of sustainability.
In its hard form, PVC is durable and used in construction projects and home appliance products. In packaging, PVC film is used for flexible applications (such as shrink film and bags).
PVC is used in the building and construction industry, as well as in the healthcare, electronics and automotive sectors. Tubing, blood bags, wire and cable insulation, car windshield system components, packaging, etc are commonly made with it. One of the common uses of PVC shrink film includes CD and DVD packaging, game and software boxes, and other non-food items.
PVC is a combination of three elements: carbon, hydrogen and chlorine. Due to the harmful smell it emits when heated, its use is recommended only in well-ventilated facilities. It is banned in some countries due to the chemical compounds and toxic by-products created during its creation and decomposition. If you are going to use PVC shrink film, make sure that the process of using it is entirely safe.
Another problem with PVC is its reaction to hot and cold temperature changes, which makes it brittle at low temperatures and wrinkles at high temperatures. PVC&#;s resistance to tearing after a puncture is high, but its resistance to puncture is low.
Due to the fragile nature of PVC shrink film, it is unsuitable for packing several products. Of course, PVC exerts a little contraction force on the products inside. Another important thing about it is its low recyclability. PVC is a level 3 recycler and is not recyclable in most cases.
Polyolefin shrink film is durable and practical and an excellent option for making all kinds of shrink film. It has replaced PVC in many applications and is a safe, FDA-approved way to package food. POF materials are available with different properties. One option is a cross-linked film, which provides high tensile strength and incredible transparency for high-speed packaging applications. Polyolefin reduces roll changes and increases efficiency and productivity. POF shrink film has good puncture resistance and sealing power, which helps protect irregularly shaped items throughout its supply chain life cycle.
Because of POF&#;s greater strength, longer rolls of film can be made with thinner gauges. Before continuing, it is necessary to be familiar with the concept of &#;Gauge&#;. A gauge is a unit of measurement equal to one-hundredth of a mile. For example, &#;70 gauge&#; refers to 70 hundredths of a mil or a thickness of 70 mil. &#;Gauge&#; can also refer to the general specification of a roll of film. POF is available in thicknesses less than 35-gauge (0.35 mil) and typically in 45, 60, 75 and 100 (1 mil) gauges.
The malleability and affordability that POF offers in packaging devices and forms make it a viable option for manufacturers of protective packaging of all sizes. In some cases, POF film needs to have small holes or seams added before application. These holes allow air to escape during the shrinking process, producing a flat pack with a shrinking surface and no air bubbles. This is why pre-punched shrink film is now available from many suppliers.
POF produce from 100% recyclable materials. With its superior transparency and glossy appearance, polyolefin shrink film is best for consumer products where the interior display is critical. It also works well for packing multiple items, such as tissue boxes. POF is durable and less affected by temperature changes. It has excellent tensile strength and the ability to be assembled quickly and completely, and as soon as it leaves the shrink tunnel, it brings the final product that is ready to be shipped and stored. Typical applications of POF film include toy packaging, candy wrappers, books, food wraps, most retail items, and any consumer product where appearance is essential.
Polyethene is a type of polyolefin, which means one, and as a result, it is a single monomer film formed by adding ethylene during polymerization. PE is a raw material for manufacturing flexible packaging, including shrink film and stretch film, for which it exhibits different properties. The three most common forms of polyethylene include high-density, low-density, and linear low-density polyethene.
This type of polyethene is less dense and has less mass than its volume. LDPE is highly resistant to impact, moisture and chemicals. It is also recyclable. LDPE is commonly used in applications where heat sealing is essential and in manufacturing flexible lids and packing.
This film is one of the most widely used films in the packaging industry. Among all types of polyethylene film, LLDPE is the most flexible. A linear form of low-density polyethylene, LLDPE offers greater strength and flexibility and provides excellent stretch. Although it doesn&#;t shrink as well as the previous ones, it&#;s great for wrapping stretch pallets and protecting heavy loads during shipping. LLDPE and LDPE films are commonly used for pallet packaging, snacks, frozen foods and pouches.
The advantages of low-density polyethene over other shrink-film packaging include greater strength and durability for heavier and more oversized items (such as beverage boxes). These videos are also printable. While POF and PVC are limited in gauge thickness (typically around 100 gauge), greater thicknesses (higher gauges) are possible with PE up to gauge (12 mils). These thicknesses are used in marine industry applications. The disadvantages of polyethene for sheeting are the shrinkage rate (usually around 20%) and less transparency.
Shrink and stretch films are often confused because they are very similar, and, as mentioned above, both can be made from polyethylene. However, each has a different function. Film sheeting is gently placed on one or more items, and applying heat gathers around them, creating a strong and durable protective layer.
Polyethene stretch film is formulated differently to be stretched around goods. The elasticity of the film, combined with its adhesive ability, makes a strong protective layer around the items. Stretch film is commonly used for palletizing or consolidating multiple items on a pallet to prevent them from shifting during shipping. Stretch film is typically stretched to about 100-300%, while shrink film is roughly stretched to about 50-75%.
The shelf life of shrink film allows us to protect and preserve the contents of the package. Cross-linked films are more resistant to tearing and punctures for goods with sharp edges, thus reducing the possibility of damage to the package during transportation. Nylon shrink is also great for reducing product manipulation. It helps to minimize product damage and waste in a vast production line. In addition, shrink film helps to increase the shelf life of perishable products and can preserve the smell of the contents inside the package.
Polyolefin coils can be produced as customized. Adding ingredients to its formula can be used to package any compact product. These films are transparent and bright, and as a result, they cause visual appeal in the supply of products; they are printable; Therefore, the Packing design improves, and the manufacturer can add special effects can be added.
One of the most significant advantages of POF and PE films is that they are recyclable. As a result, they do not harm the environment and are entirely green. In addition, unlike PVC, POF shrink film does not release harmful fumes during heat-sealing.
Many brands have eliminated cardboard packaging by taking advantage of the strength and durability of nylon shrink. Heavy products can be safely packed without the need for cartons. Considering that the layer of shrink is thin, as a result, the space required for storage will be reduced, and more goods can be stored in the warehouse. On the other hand, nylon shrink is cheap, so the final production costs will also be reduced. Packing with them is also very easy, and labour is less tiring.
Pooshan Plastic shrink film can be ordered with a thickness of 35 to 150 microns and a final width of mm. Another advantage of our films is the ability to print; of course, you can also order the film in colourful and transparent.
Are you interested in learning more about pet shrink films market? Contact us today to secure an expert consultation!