The reason why substrates using flexible packaging polyurethane lamianting adhesives need to undergo corona treatment
2026,07,07
In the production of flexible packaging, BOPP, CPP, PE and other plastic substrates are commonly used materials for lamination processing. These substrates have strong chemical inertness, extremely low polarity and low surface tension. If polyurethane laminating adhesive is directly applied, the adhesive is difficult to evenly wet and spread, and cannot form a firm bond. This easily leads to problems such as lamination delamination, blistering, and insufficient peel strength. Therefore, before bonding with polyurethane laminating adhesive, the substrates must undergo corona treatment.
Corona treatment is an efficient surface activation process. It ionizes air through a high-frequency and high-voltage electric field, generating ozone and active oxygen atoms. These highly oxidizing active particles bombard the surface of the substrate, breaking the chemical bonds of the surface layer molecules of the material. At the same time, they oxidize and generate polar groups such as hydroxyl and carbonyl, significantly increasing the surface tension and polarity of the substrate, and enhancing the molecular bonding force with polyurethane lamianting adhesives.
Meanwhile, corona discharge can remove weak interface impurities such as oil and dust from the surface of the substrate, optimize the microstructure of the surface layer, and enable the adhesive to fully penetrate and adhere to the substrate. Polyurethane laminating adhesives contain polar amide bonds. After the substrate is activated by corona discharge, it can form a stable physical bond and chemical combination with the adhesive, significantly enhancing the bonding strength and weather resistance of the composite film.
In conclusion, corona treatment can completely solve the problem of difficult adhesion of non-polar plastic substrates, and is a key pre-treatment process for ensuring the stable quality and eliminating adhesive defects in the production of flexible packaging lamination.
