Shrink Film Packaging and Process Overview

Editor's note: Shrink film is a thermoplastic film that is stretch oriented during production and shrinks during use. The heat shrinkability of the film was applied as early as 1936. Initially, rubber films were used to shrink the packaging of perishable foods. Nowadays, heat shrink technology has been developed to almost all kinds of goods packed with plastic shrink film. In addition, shrink packaging is also used to make shrink labels and shrink caps so that containers that are not easily printed or have a complex shape can be labeled. Recently, new and updated application areas have been developed.

How large is the market for shrinkwrap and shrink labels? At present, the sales revenue of heat-shrinkable film packaging is about 200 million U.S. dollars. According to relevant information, the sales revenue of heat-shrinkable film bottles will increase to 300 million U.S. dollars in the next few years, so the industry should at least turn one at a time. Fan. Other industry applications (such as cans, batteries, etc.) of heat-shrinkable film packaging have actually begun before this, although these markets are not as fast as the bottle, but the annual growth rate has reached 30%. .

Based on the application hotspots of shrink film, we discuss the topic of shrinking film, the main points of design process, and the application of new product development.

Shrink film material and selection>>>

â– Main material

The materials used for the heat shrinkable film are mainly various thermoplastic films. Initially, PVC shrink film was the main product. With the continuous development of market demand, PVC shrink film gradually decreased, and various kinds of PE, PP, PET, PVDC, POF and other multi-layer co-extrusion heat shrinkable films developed rapidly and became mainstream in the market.

The materials used to make shrink film sleeve labels include PVC (polyvinyl chloride) film, PET (polyester) film, PETG (modified polyester) film, OPS (orientated polystyrene) film, and its properties are as follows:

1 PVC film: PVC film is currently the most widely used film material. Its price is extremely low, the range of temperature shrinkage is large, and the requirement for heat source is not high. The main processing heat source is hot air, infrared rays or a combination of both. However, PVC is difficult to recycle and produces poisonous gas when it burns. This is not conducive to environmental protection. It has been banned in Europe and Japan.

2OPS Membrane: As an alternative to PVC film, OPS film is increasingly used. It has good shrinkage performance and is also conducive to environmental protection. Now the product has already been in short supply in the domestic market. At present, the high-quality OPS film is still mainly dependent on imports, which has become an important factor constraining its development.

3 PETG film; PETG copolymer film is not only conducive to environmental protection, but also can adjust the shrinkage rate in advance. However, due to excessive shrinkage, it is also limited in use.

4PET film: PET film is an internationally recognized environmentally friendly heat shrinkable film material, its technical specifications, physical properties, application range and use methods are close to PVC heat shrinkable film, but the price is cheaper than PETG film, is the most advanced single The shrink film has a transverse shrinkage of 70%, a longitudinal shrinkage of less than 3%, and is non-toxic and non-polluting. It is the ideal material for replacing PVC film.

In addition, the heat-shrinkable film tube is also a material for producing a shrink film sleeve label, and can be molded at one time without sewing in production. Compared with horizontally flattened films, the use of heat-shrinkable film sleeves has a lower cost and the surface of the tube body is harder to print. At the same time, the graphic of the heat-shrinkable film tube label can only be printed on the surface of the film, and the graphic is easily worn during transportation and storage, which affects the entire packaging effect.

â– Selection points

The customer will usually first consider the specific selection mode from the cost. Heat-shrinkable packaging and laminating films can usually achieve the same packaging effect. How to decide which packaging film to use? ? In general, the main differences lie in the requirements for packaging patterns, the frequency of packaging required, the shelf life requirements, and the physical properties of the packaging itself such as liquids, powders, granules, solids, squares, and the like.
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BOPP shrink film for cigarettes (top) (middle) (bottom)

Shrink film features, processes and applications >>>

Shrink film production is usually carried out by extrusion blow molding or extrusion casting to produce thick films, then longitudinal and transverse stretching, or only one of them, at a high elastic temperature above the softening temperature and below the melting temperature. The orientation is oriented in the direction of stretching, while it is not stretched in the other direction. The former is called biaxial stretching and shrinking film, and the latter is called unidirectional shrinking film. In use, a reliable shrinkage force wraps the packaged product at or near the stretching temperature.

â– Main features

1) beautiful appearance, close to the goods, it is also called body packaging, suitable for a variety of different shapes of the product packaging;
2) Good protection, if you combine the shrink-wrapped inner package with the transport package hanging on the outer package, you can have better protection;
3) Good cleaning, especially suitable for precision instruments, high-precision electronic components packaging;
4) Good economy;
5) Good burglary resistance. A variety of foods can be packed together with a large shrink film to avoid loss.
6) The stability is good, and the goods will not fall in the packaging film;
7) Transparency is good, customers can see the content of the product directly.

â– Process points

The shrinkable label has strong adaptability, and can be decorated on plastic, wood, paper, metal, glass, ceramics and other packaging containers, and is widely used in beer beverages, medicine and health care, daily chemical products, snack foods, stationery and other fields.

In order to achieve the best overall labeling effect, not only the heat shrinking temperature of the labeling machine has to be adjusted, but also the selection of the label material and the design pattern is also crucial.

1. Label Design The design of the decorative pattern on the film sleeve is determined according to the thickness of the film. When designing a pattern, it is first necessary to ascertain the transverse and longitudinal shrinkage of the film, and the allowable shrinkage in all directions after packaging and the allowable deformation error after the shrinkage of the decorating pattern to ensure that the contracted pattern and text can be accurately restored.

2. Film Thickness and Shrinkage The materials used to shrink the film sleeve labels must consider three factors: environmental protection requirements, film thickness, and shrinkage properties.

The basis for determining the film thickness is the application field and cost factor of the label. Of course, price is not a decisive factor, because each film has its own uniqueness. Users and trademark printers must specify the film used and the most suitable materials before signing the contract. In addition, the indicators required by the processing equipment and other process factors also directly affect the choice of thickness. It is generally required that the film thickness of the shrink film sleeve label is 30 to 70 μm, and 40 μm and 50 μm films are used more frequently. In addition, there is a certain requirement for shrinkage of the film, and the transverse (TD) shrinkage is higher than the longitudinal (MD) shrinkage. The transverse shrinkage of commonly used materials is 50% to 52% and 60% to 62%, and in special cases it can reach 90%. The longitudinal shrinkage requirement is 6% to 8%. When making labels for shrink film sleeves, choose a material with a small longitudinal shrinkage.
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