- Material selection and performance
The winding film must have high toughness, puncture resistance, and good self-adhesiveness, so the selection of raw materials is crucial.
The molecular structure of linear low-density polyethylene (LLDPE) resin is chain like, with a narrow relative molecular weight distribution and short but few branched chains. The structural characteristics give it excellent physical properties, such as impact strength, puncture resistance, and good resistance to low-temperature impact. If processed properly, it also has good self-adhesiveness. Due to these characteristics meeting the performance requirements of the winding film, LLDPE was chosen as the raw material.
In addition, the melt flow rate (MFR) and density of LLDPE are closely related to the film properties. If the MFR value of the resin is too high, it will cause a decrease in the puncture resistance and low self-adhesion of the film; On the contrary, thin films are difficult to form and can easily cause serious shrinkage, affecting production efficiency. After repeated experiments, it was found that the optimal MFR value for LLDPE is around 2g10min. - Product structure design
The winding film is divided into two types: double-sided adhesive winding film and single-sided adhesive winding film. The double-sided adhesive wrapping film has excellent self-adhesive properties on both sides, making it suitable for wrapping and packaging items with edges and corners. The film is not affected by the edges and corners of the items, and the tying operator can freely adjust the stretching force to keep the goods as one unit; One side of the single-sided adhesive winding film has excellent self-adhesiveness, while the other side is smooth, suitable for palletless packaging, carpet and green storage feed wrapping, etc.
The multi-layer co extrusion salivation method can produce the above two types of winding films, with three structures: A/A2/A3, A1/B/A2, and ABC (A, B, and C are three materials). Usually, the structure of thin films is designed according to the requirements of their use. For example, the structure of double-sided adhesive wound films is AB/A, mainly considering that the outer resin (A layer) must have viscosity and toughness, and the middle resin (B layer) must have load retention and compatibility, etc. This structural design can fully meet the requirements of double-sided adhesive wound films. In short, the biggest advantage of co extrusion salivation method is to integrate the excellent characteristics of various materials together, thereby meeting the requirements of packaging various items and making the application field more extensive.
