What Is a Shrink Film?
Shrink film is a film that shrinks when heat is applied. The film is made of thermoplastic resin that can repeatedly deform with heat. In addition to having high gloss and transparency, it also has excellent water resistance, cold resistance, and mechanical strength. Applying these properties and its ability to shrink with heat to fit various shapes, it is used for packaging applications with excellent aesthetics. Shrink film is also often used to protect products and prevent tampering these days because of its irreversible nature once it is torn.
Uses of Shrink Films
Shrink film is used for a wide variety of packaging applications. It is helpful for packaging applications because of its superior design, product protection, and work efficiency.
1. Design
Because it can provide a large display area, product PR and multi-color printing are possible. It is used for boxed tissues and instant noodle packaging.
2. Product Protection and Tamper-Resistance
It is used for its superior water resistance and cold resistance, as well as for proof of unopened packages, and mainly for packaging caps.
3. Work Efficiency
It combines multiple products into one to improve work efficiency and convenience, such as yogurt, 6-packs of PET bottles, etc.
Principle of Shrink Films
This section introduces the characteristics of each material used in shrink film. The advantages and disadvantages of the six primary materials used are explained below.
1. Polyvinyl Chloride
It has excellent transparency, formability, flame resistance, and electrical insulation properties and can shrink at low temperatures. On the other hand, its natural shrinkage and fragile sealing surface are disadvantages.
2. Polypropylene
Polypropylene has excellent transparency, cold resistance, moisture resistance, and printability and has a low unit price. On the other hand, it has the disadvantage of natural shrinkage.
3. Polyethylene
Polyethylene has higher mechanical strength than polypropylene. Its good shrinkage enables large blocking packages. However, it is less transparent than other types.
4. Polystyrene
Superior transparency and heat shrinkability, but weak against impact and organic solvents.
5. Polyolefin
Polyolefin has a high shrinkage rate and is excellent for its finish, as it does not easily wrinkle or form a crease. It is also a highly convenient material with high tearing strength. Although polyolefin offers high performance, its unit price is high.
6. Polyethylene Terephthalate
Known popularly as PET, this resin has excellent transparency, mechanical strength, chemical resistance, and dimensional stability. It has various exceptional properties, but its difficulty processing is a drawback.