The Effect of the Friction Coefficient of BOPA Film on Quality

Generally, the friction coefficient μs of the treated surface of BOPA film is between 0. 4~0. 7.

The friction coefficient of BOPA film is divided into kinetic friction coefficient and static friction coefficient.

In the production process of BOPA film, the friction coefficient of plastic film is an important technical indicator. On the one hand, together with the anti-blocking performance of the film, it serves as a quantitative evaluation index of the openness of plastic film; on the other hand, it can also serve as one of the reference data for the running speed of automatic packaging machines, tension adjustment, and wear during film running.

The magnitude of the friction coefficient can be controlled through the selection and amount of additives. For automatic packaging products, the friction coefficient of the side of the film in contact with the equipment is preferably between 0. 25~0. 30.

Generally, when BOPA film is used as the printing surface, due to the need for fast coding in post-processing, the friction coefficient of the untreated surface of the film should be below 0.25. If the friction coefficient is too large, the film will encounter greater resistance in use and is prone to film breakage and rupture. As the additive content in the film increases, the friction coefficient of the film decreases and the haze increases.

In the processes of printing and aluminum metallizing, there are likewise certain requirements for the friction coefficient of plastic film.

Reducing the friction coefficient of the film surface is beneficial to printing and aluminum metallizing, helps to increase the bonding surface between them and the plastic film, and helps to improve the adhesive force between them. The magnitude of the friction coefficient is likewise adjusted through the use of additives. Therefore, before the film leaves the factory, the friction coefficient between the film surface and the metal (stainless steel) surface must be tested. In case of high-humidity and high-temperature weather or for products requiring high-speed coding, the BOPA film surface is required to have not only low hygroscopicity but also a low surface friction coefficient; the surface friction coefficient of ultra-high-slip BOPA film can generally be controlled between 0.15~0.25.

The reason for the continuous decrease in the friction coefficient of the film is that the slip agent continuously 'migrates' to the film surface and covers an increasing area of the film surface. If the slip agent that has already 'migrated' to the surface of the PE film 'disappears' or 'decreases' for some reason, the result will be an 'abnormal rise' in the surface friction coefficient of the PE film.

If the slip agent content is too high, it will also affect the printability of the film, which is extremely unfavorable to printing. Therefore, the film surface should have suitable slip to ensure that high-speed printing can be carried out smoothly. At room temperature, the kinetic friction coefficient of the untreated surface of ordinary BOPA film is generally required to be between 0.2~0.4 (excluding the requirements for films used for fast coding). The kinetic friction coefficient of the corona-treated surface of BOPA film is generally not higher than 0.7, so that the probability of failure in use is lower. (This article is excerpted from 'Corona Treatment and Surface Properties of BOPA Film', author: Chen Mengjie; the full text has been published in Packaging Frontier. For more technical content, please see Packaging Frontier or the Packaging Frontier information website www.pack168.com. If you have different opinions, you are welcome to continue the discussion at www.pack168.com; friends who provide more solutions can obtain reading credits for technical articles on the website. To request credits, please contact Xiaoyang: 15813331361, Xiaolai: 18475695660)