Cross-linked shrink film: In-depth analysis of stretching process and excellent performance

In the field of packaging materials, cross-linked shrink film has become an indispensable packaging solution for many industries with its unique physical properties and wide application fields. Its excellent performance, especially shrinkage performance, is largely due to the fine stretching process during the production process.

The production of cross-linked shrink film begins with the chemical reaction of specific polyethylene raw materials. These raw materials undergo a specific cross-linking reaction to form polyethylene blocks with a cross-linked structure. These block materials are then fed into a heating device and precisely controlled to reach a suitable molten state. In the molten state, the polyethylene blocks are pressed and stretched into a continuous film.

This preliminary film preparation process is crucial for subsequent stretching treatment. It requires not only a certain thickness and uniformity of the film, but also a certain orderliness of the molecular chain structure inside the film so that it can be effectively rearranged during the stretching process.

After the film is prepared, the next stretching step is the most critical part of the cross-linked shrink film production process. The stretching process is to stretch the film uniformly and stably to a predetermined length. This step seems simple, but it actually involves complex physical and chemical changes, which have a decisive influence on the final performance of the film.

The stretching treatment first makes the thickness of the film more uniform through the action of mechanical force. During the stretching process, the thickness of the film will gradually decrease along the stretching direction, while the thickness perpendicular to the stretching direction will remain unchanged or slightly increase. This change in thickness makes the film flatter and more uniform overall, thereby improving its aesthetics and practicality.

Another important effect of the stretching treatment on the performance of the film is the rearrangement of the molecular chains. During the stretching process, the molecular chains inside the film will be oriented by the mechanical force. This oriented arrangement not only enhances the strength and toughness of the film, but also improves its tear resistance and puncture resistance. At the same time, the oriented arrangement of the molecular chains also helps to improve the thermal shrinkage performance of the film, so that it can tightly wrap the packaged items along the stretching direction when heated.

The most significant performance that the stretching treatment gives to the cross-linked shrink film is its excellent shrinkage performance. When the film is heated, its molecular chains will shrink along the stretching direction. This shrinkage is uniform and stable, which can ensure that the film tightly wraps the packaged items to form a firm packaging structure. At the same time, the tension generated during the shrinking process also helps to improve the sealing and moisture resistance of the packaging, thereby extending the shelf life of the packaged items.

Although stretching treatment is crucial to the performance of cross-linked shrink films, this process also faces many challenges. For example, the selection and control of parameters such as stretching speed, stretching ratio and temperature directly affect the final performance of the film.

Stretching speed is one of the key factors affecting film performance. Too fast stretching speed may cause stress concentration and defects inside the film, thereby reducing its strength and toughness. On the other hand, too slow stretching speed may make the shrinkage performance of the film insufficient and unable to meet the packaging requirements. Therefore, during the production process, it is necessary to accurately control the stretching speed according to factors such as the material and thickness of the film.

The stretching ratio refers to the length change rate of the film during the stretching process. A suitable stretching ratio can ensure that the film will neither be over-deformed nor under-deformed during the stretching process. Too large a stretching ratio may cause the film to crack or break during the shrinking process, while too small a stretching ratio may make the shrinkage performance of the film insufficient. Therefore, when selecting the stretching ratio, it is necessary to comprehensively consider factors such as the material, thickness and packaging requirements of the film.

Temperature is another important factor affecting the effect of stretching treatment. During the stretching process, the film needs to be kept within a certain temperature range to ensure that its molecular chains can be effectively rearranged. Too high a temperature may cause the film to soften excessively or even melt, thus affecting its stretching effect and final performance; while too low a temperature may prevent the molecular chains of the film from fully moving, resulting in poor stretching effect. Therefore, during the production process, the temperature of the heating and cooling systems needs to be precisely controlled to ensure that the film maintains a suitable temperature during the stretching process.

With its excellent shrinkage performance, strength and toughness, as well as good transparency and gloss, cross-linked shrink film has been widely used in the packaging industry. It can not only be used for the packaging of goods such as food, beverages, and medicines, but also for the packaging of precision items such as electronic products and crafts. In addition, cross-linked shrink film can also be used as a protective film to protect glass, metal and other items from scratches and contamination.

With the advancement of science and technology and the continuous improvement of people's requirements for the performance of packaging materials, the production process and performance optimization of cross-linked shrink film will continue. For example, by improving the stretching process and developing new cross-linking agents, the shrinkage and mechanical properties of the cross-linked shrink film can be further improved; at the same time, by introducing environmentally friendly materials and degradable materials, the impact of the cross-linked shrink film on the environment can also be reduced.

Stretching is the most critical part of the production process of cross-linked shrink film. It not only makes the thickness of the film more uniform, but also enhances the strength and toughness of the film by rearranging the molecular chains, and gives the film excellent shrinkage properties. However, the stretching process also faces many challenges and areas that need to be optimized.