First, the surface cleanliness of the film is crucial. If there is oil, dust or other impurities on the surface of the film, it will hinder the close bonding of aluminum atoms with the polypropylene surface during the aluminizing process and reduce the adhesion. For example, in the case of poor production environment or improper storage of raw materials, impurities are easy to adhere to the surface of the film, affecting the subsequent aluminizing effect.
Secondly, the crystallinity of the polypropylene film will also affect the adhesion. Higher crystallinity will make the surface of the film more regular and dense, which is not conducive to the penetration and adhesion of aluminum atoms. Because the molecules in the crystalline area are closely arranged, there are relatively few active sites for aluminum atoms to bind, resulting in decreased adhesion.
Furthermore, the aluminizing process parameters are key factors. Such as evaporation temperature, evaporation rate, vacuum degree, etc. If the evaporation temperature is too high or the evaporation rate is too fast, aluminum atoms may not be evenly deposited on the surface of the film, forming a loose aluminum layer structure with weak bonding with the film; and insufficient vacuum may introduce impurity gases, affecting the purity and adhesion of the aluminum layer.
In addition, the selection and use of primers should not be ignored. Suitable primers can form chemical bonds between the film and the aluminum layer to enhance adhesion. However, if the type of primer does not match or the coating process is improper, such as uneven primer thickness and insufficient drying, it will affect adhesion.
In view of these influencing factors, the following improvement measures can be taken. Before production, strengthen the cleaning treatment of the surface of the vacuum aluminized cast polypropylene composite film, and use physical or chemical methods to remove oil and impurities to ensure the surface is clean.
For the crystallinity problem, the crystallinity of the polypropylene film can be appropriately reduced and the surface active sites can be increased by adjusting the processing parameters, such as lowering the processing temperature or increasing the cooling rate.
Optimize the aluminizing process, accurately control the evaporation temperature, rate and vacuum, and determine the best combination of process parameters through experiments to ensure uniform deposition and good adhesion of the aluminum layer.
In terms of primer, choose a primer that has good compatibility and reactivity with both polypropylene and aluminum, and apply it in strict accordance with the operating procedures to ensure the quality and effect of the primer, thereby effectively improving the adhesion of the vacuum aluminized cast polypropylene composite film, meeting its application needs in food packaging, electronics and other fields, and improving the quality and performance stability of the product.
