What is the Heat-shrinkable Film?

What is the Heat-shrinkable Film?

• For the sale and transportation of various products, its main function is to stabilize, cover and protect the product.
• Shrink film is a thermoplastic that is stretched and oriented during production and shrinks when heated during use. The shrink film must have high puncture resistance, good shrinkage, and certain shrinkage stress.
• During the shrinking process, the film must not create holes.
• If the shrink film is often used outdoors, a UV anti-ultraviolet agent needs to be added.

What are the Types of Heat-shrinkable Film?

Shrink film can be divided into PVC, POF, OPS, PE, and PET.

1. PVC Shrink Film:
   PVC shrink film has additional ingredients to enhance its heat resistance, toughness, ductility, etc. The top layer of this surface film is lacquer, the main component in the middle is polyvinyl chloride, and the bottom layer is a back coating adhesive. It is a synthetic material that is widely used today. Among the materials that can produce three-dimensional surface films, PVC is the most suitable material. Due to the unique properties of PVC (rainproof, fire resistance, antistatic, easy to form) and the characteristics of low input and high output PVC, it is widely used in the building materials industry and packaging industry. Therefore, PVC film has high transparency, good gloss, and shrinkage.
2. POF Shrink Film:
   POF is a multi-layer co-extruded environmentally friendly polyolefin heat shrinkable packaging material. The components of POF shrink film are PE and PP. Different from PVC, POF is a soft and environmentally friendly shrink film, which will not release toxic gas during the burning process, and can be in direct contact with food. POF shrink film is co-extruded by multi-layer PE or PP film, which makes POF have a variety of different characteristics, such as soft texture, toughness, high transparency, high shrinkage rate, etc. It is widely used in the international market. Environmentally friendly heat shrinkable film packaging material approved by the European and American markets. The Features of POF Packaging Film:
   • High shrinkage rate.
   • High gloss, high transparency, and good decorative properties.
   • Good flexibility, no embrittlement at low temperature, and not easy to age.
   • The product density is low, which can effectively reduce the packaging cost.
   • Outstanding heat-sealing performance and high sealing strength.
   • Good tear resistance and puncture resistance.
   • Wide range of use, can be used for a semi-automatic, fully automatic high-speed packaging equipment, and manual packaging.
   • The products comply with FDA and USDA standards, are non-toxic and environmentally friendly, and can be used in the packaging production of various products such as food and medicine.
3. OPS Shrink Film:
   OPS is a type of skin packaging material that meets environmental protection requirements. OPS heat shrinkable film has high strength, high rigidity, stable shape, and good gloss and transparency. It is easy to process, easy to color, has good printing performance, and has a high printing resolution. For trademarks that constantly pursue exquisite printing, it is a complete improvement in the material. Due to the high shrinkage rate and strength of OPS film, it can be closely attached to containers of various shapes, so it can not only print beautiful patterns but meet the use of various novel packaging containers with different shapes.
   • OPS can achieve a lateral shrinkage rate of about 74%, and it is not easy to wrinkle during the shrinkage process. The shrinkage can be completed in a non-high temperature environment so that the heat-shrinkable label can be packaged on the outside of the container. After the horizontal shrinkage of the label is completed, the height of the label is hardly shortened in the vertical direction due to the vertical shrinkage.
   • OPS hardly generates crystal points. Since OPS resin is different from PVC resin in the raw material refining process, it can greatly reduce the existence of crystal points and foreign matter.
   • The specific gravity of OPS is light, and the specific gravity of OPS is only 1.05. For the three materials of OPS, PVC, and PET with the same thickness and the same area, OPS can reduce the weight by 25%.
   • The tear line made after shrinking the OPS label is very symmetrical and easy to tear without destroying the overall effect of the label.
4. PET Heat Shrinkable Film:
   PET heat shrinkable film is a new type of heat shrinkable packaging material. Because it is easy to recycle, is non-toxic, tasteless, and has good mechanical properties, especially in line with environmental protection and other characteristics, polyester (PET) has become an ideal substitute for polyvinyl chloride (PVC) heat-shrinkable film in developed countries.
   • Unitization: This is one of the biggest characteristics of shrink film packaging. With the help of the super-strong winding force and retractability of the film, the products are compactly and fixedly bundled into a unit, so that the scattered small parts become a whole. Even if in unfavorable environments, the product does not have any looseness and separation, and there is no sharp edge and stickiness to avoid damage.
   • Primary protection: The primary protection provides the surface protection of the product, forming light and a protective appearance around the product, to achieve the purpose of dustproof, oil-proof, moisture-proof, waterproof, and anti-theft. It is particularly important that the wrapping film packaging makes the packaged items evenly stressed to avoid damage to the items caused by uneven stress.
   • Compression fixation: The product is wrapped and packaged by the retraction force of the stretched film to form a compact unit that does not occupy space so that the pallets of the product are tightly wrapped together, which can effectively prevent transportation. During the process, the products are dislocated and moved, and the adjustable tensile force can make the hard products close to each other and the soft products tighten.
   • Cost saving: The use of stretch film for product packaging can effectively reduce the cost of use. The use of stretch film is about 15% of the original box packaging, about 35% of the heat-shrinkable film, and about 50% of the carton packaging. At the same time, it can reduce the labor intensity of workers, and improve the packaging efficiency and packaging grade.
5. PVC Shrink Film:
   PE is a transparent thermoplastic. PE heat shrinkable film is widely used in the whole package packaging of wine, cans, mineral water, various beverages, cloth, and other products.

What is the Chemical Principle of Heat Shrinkable Film Production?

The shrinkage of the heat-shrinkable film after heating is a physical phenomenon. Simply put, the thermal motion of the molecules causes the film to shrink. In common plastic films, the macromolecular chains in the chemical structure are in a state of natural curling, and generally do not shrink when heated. After the raw material is melted, the film is stretched at a specified temperature and under the action of external force, so that the macromolecules cannot slip with each other, and the unnatural state is frozen. At room temperature, the macromolecules in the plastic film have poor mobility, and this unnatural state cannot be eliminated by molecular motion, which is why the heat-shrinkable film does not shrink at room temperature.

It is a process of entropy reduction from raw materials to generating heat-shrinkable film, and the thermodynamic state of heat shrinkable film is unstable. In other words, after the film is preheated, it is stretched, cooled, and shaped (if it is not subjected to heat setting treatment) to obtain a heat-shrinkable film.

Why Does the Heat-shrinkable Film Shrink After Heating?

When the heat-shrinkable film is reheated to a certain temperature, the frozen macromolecules will start to move again, and try to recover from the unnatural state to the natural state. As a result, the molecular chain will quickly return to the random coil shape, and the film will shrink. Such a process seems to be essentially the same as a stretched rubber band that relaxes and then springs back.

How to Make a Heat-shrinkable Film with a Higher Shrinkage Rate?

Data for evaluating heat-shrinkable films include shrinkage rate, shrinkage tension, and shrinkage temperature. If you want to obtain a film with a higher shrinkage rate, it is necessary to choose a polymer resin with low crystallinity or a low crystallinity.

In terms of polymer chemistry, according to the degree of crystallinity, it can be divided into amorphous polymers, semi-crystalline, and liquid crystalline polymers. The molecular chain in the amorphous region is easy to shrink after being heated, the required temperature is lower and the time is shorter. While the molecular chain in the crystalline region needs to destroy the lattice to achieve shrinkage, the temperature needs to be raised to the vicinity of the melting point, and the relaxation time of the molecular chain is longer, which is not possible during the use of shrink film.

For heat-shrinkable films made of the same material, the higher the proportion of amorphous regions. The greater the shrinkage rate and the greater the shrinkage force. Heat shrinkable films with more amorphous regions require lower shrinkage temperatures.

How to Choose Heat Shrinkable Film?

When picking a heat-shrinkable film, make sure:

• What tool is used to use the heat-shrinkable film.
• What is the size and weight of the product.
• How much temperature the product can withstand, and choose the most suitable heat shrinkable film more accurately.

The Scope of Application of Heat Shrinkable Film:

Heat shrinking uses far-infrared radiation to directly heat various specifications of films. The products are transported to the shrinking furnace through the conveyor belt, and the products are loaded with shrink wrapping films. After sealing, they enter the shrink-wrapping machine, and the products shrink automatically. It does not affect the packaging, electronic step-less speed change, solid-state voltage regulator temperature control, stable and reliable, and suitable for heat shrinkage of food, beverages, candy, stationery, hardware tools, daily necessities, chemical products, etc.

Heat shrinkable film is widely used in the outer packaging of various products such as food, medicine, disinfection tableware, stationery, craft gifts, printed matter, hardware, and plastic products, telephones, electronic appliances, and so on. Especially in the combined (cluster) packaging of irregular-shaped articles or commodities, it can not only meet the functions of moisture-proof and dust-proof, anti-touch and stealth replacement, and transparent display of commodities. It can increase the attractiveness of the appearance of the product and can be used to replace various types of cartons, which not only saves packaging costs but conforms to the packaging trend.