Winding film, also called stretch film, contraction film. In the beginning, PVC was used as the plate and DOA as the viscosifier to produce PVC winding film with self-adhesive effect. Because of environmental pollution problems, cost increase (relative PE ratio is important, the total packaging area of the enterprise is less), poor ability to pull, etc., China in 1994-1995 to produce PE stretch film gradually phased out. PE stretch film used EVA as self-adhesive raw materials at first, but its cost increased and it had peculiar smell. Later development trend used PIB and VLDPE as self-adhesive raw materials, and the plate is now dominated by LLDPE, including C4, C6, C8 and metallocene PE (MPE).
In the initial stage, the LLDPE stretch film was mainly blown by the film blowing machine, which grew from single side to two or three layers. Nowadays, LLDPE stretch film is dominated by the flow method, which is due to the advantages of thickness symmetry and high clarity in the production of flow extension line, which can be applied to the provisions of polymer cell pre-stretching. Because single-sided flow extension can not do single-layer adhesive, the main use suffers limitation. Single, two layer flow extension in the raw material selection is not three layer flow extension, secret recipe cost is also high, so or three layer co-extrusion structure is more ideal. High quality stretch film should have high definition, high vertical elongation, high yield limit, high transverse tear compressive strength, good puncture properties and other characteristics.
Classification of wound film
At present, winding film in the market can be divided into hand-wound film and machine-belt winding film according to their main uses. The thickness of hand-wound film is generally in the range of 15μ-20μ. The thickness of machine-wound film is in the range of 20μ-30μ. According to the packing method, the wrapping of lashen winding film can be divided into hand-pulled lashen packaging, vibration reduction lashen packaging and pre-lashen packaging. According to the material classification, winding film can be divided into high pressure polyethylene winding film, polyethylene winding film, butadiene-butyl acrylate winding film and so on. At present, many winding films produced and applied are made of linear high pressure polyethylene as the basic raw material, and high pressure polyethylene winding films have become popular. According to the structure of the film, the winding film can be divided into single-side winding film and double-layer winding film. Generally, only one side is sticky, so it is often called single-layer sticky winding film. With the improvement of film production equipment and technology, the advantages of double-layer winding film, which is beneficial to improving product quality and reducing production cost, have become increasingly prominent. At present, the development trend of single-sided winding film has gradually decreased. According to the forming production and processing methods are different, winding film can be divided into injection winding film and flow winding film, flow winding film characteristics are better. According to the classification of application fields, wrapping film can be divided into wrapping film of industrial supplies (such as household appliances, machinery and equipment, chemicals, decorative building materials, etc.), wrapping film of agricultural and animal husbandry packaging bags and wrapping film of household packaging bags.
Winding film raw material
The key raw material of the winding film is LLDPE, and the model key involved is 7042. Due to the unique requirements of the film, 7042N, 1018HA, 1002YB, 218N and 3518CB can also be used.
Main uses of winding film
As an indispensable part of freight transportation, winding film has the effect of fixed goods. It is widely used in papermaking industry, freight logistics, chemical plants, plastic raw materials, decorative building materials, food, laminated glass and other layers. It is also involved in export trade, paper industry, hardware, plastic chemical industry, decorative building materials, food pharmaceutical industry and other industries. It can be said that as long as there are objects in the interior space migration area, there will be the existence of the shadow of winding film.