Flexible packaging polyurethane laminating adhesives are the core materials for lamination film processing. Their resistance to various media directly determines the structural stability and service life of packaging products during storage and use, and are the key indicators for evaluating the comprehensive performance of adhesives. Flexible packaging often comes into contact with complex media such as oils, acids and bases, food ingredients, chemical auxiliaries, and electrolytes. It is prone to problems such as gelation of the adhesive layer, delamination, and attenuation of bonding strength. Therefore, the resistance to media is of crucial importance.
After curing, polyurethane laminating adhesives form a dense cross-linked structure. The soft and hard segments work together, giving them excellent resistance to various media. They can effectively resist the erosion of food soups, cleaning solvents, weak acid and alkali solutions, etc. For high-quality products, after being immersed in media, the retention rate of bonding strength can reach over 90%, maintaining the integrity of the lamination film and preventing problems such as packaging leakage and damage. Compared with ordinary adhesives, it has the characteristics of water resistance, oil resistance and aging resistance, and is suitable for various working conditions such as high-temperature boiling and normal temperature storage.
The media resistance of adhesives is significantly influenced by the raw material system and the degree of cross-linking. The polyether polyol system has outstanding hydrolytic resistance, while the polyester system has better mechanical properties and oil resistance. Increasing the cross-linking density can further enhance the resistance to chemical corrosion. Currently, the industry mainly optimizes performance through modification processes to meet the needs of various fields such as food, cosmetics, and new energy for soft packaging, providing a core guarantee for the long-term safe and stable use of packaging.
