The mainstream classification and performance characteristics of flexible packaging polyurethane laminating adhesives

Flexible packaging polyurethane laminating adhesives are the core auxiliary materials for the production of flexible laminated packaging in industries such as food, cosmetics, and medicine. With excellent adhesion, flexibility, and weather resistance, they have become the preferred adhesive products for laminating various substrates such as films, aluminum foil, and paper. In the industry, based on the raw material structure and system characteristics, they are mainly divided into two mainstream categories: polyester type and polyether type. The performance of these two types is significantly different, and they are suitable for different production scenarios. 

 

Polyester-based polyurethane laminating adhesives are the most widely used. Their molecular chains contain polar ester groups, and the intermolecular forces are strong. They have excellent adhesion to polar substrates such as PET, nylon, and aluminum foil. This type of adhesive has high bonding strength, good heat resistance, outstanding resistance to boiling and aging, and can meet the production requirements for high-temperature sterilization and water-boiling packaging. It is widely used in laminated packaging for high-temperature food. However, it has relatively weak low-temperature toughness and is prone to brittleness in long-term low-temperature environments. 

The polyether-based polyurethane laminating adhesive is mainly composed of ether bond structures. Its molecular chain has extremely strong flexibility and excellent low-temperature adaptability. It can maintain stable bonding performance in extremely low temperatures and is not prone to cracking or delamination. At the same time, it has outstanding hydrolysis resistance and is suitable for use in high-humidity and high-humidity environments. It is commonly used in the production of frozen food and fresh flexible packaging. However, its bonding strength and heat resistance are slightly inferior to those of the polyester type, and it is not suitable for high-temperature processing conditions. 

 

Currently, the industry typically selects equipment based on the requirements of the packaging terminals. For high-end laminated packaging, two systems are often combined to balance both high and low temperature performance as well as bonding stability, thus meeting the diverse production needs of flexible packaging.