Discussion on the Heat Resistance of Flexible Packaging Polyurethane Laminating Adhesive
2026,05,12
Flexible packaging polyurethane laminating adhesives are the core material for film composites. Their heat resistance directly determines the stability of flexible packaging products during high-temperature boiling, heat sealing processing, and high-temperature storage conditions, and is a key indicator for evaluating packaging quality. Ordinary polyurethane laminating adhesives have excellent adhesion performance at room temperature, but they have shortcomings in heat resistance. In high-temperature environments, they are prone to molecular chain relaxation and cross-linking structure disruption, which can lead to composite film delamination, decreased peel strength, and blistering.
The heat resistance of polyurethane laminating adhesives is determined by their molecular structure. The ratio of the soft segment to the hard segment and the crosslinking density are the core influencing factors. The heat resistance of conventional products is mostly between 80–100℃, and they are only suitable for normal ambient temperature packaging.However, in scenarios such as food steaming and high-temperature sterilization, which require a temperature of 121–135℃, ordinary laminating adhesives are prone to thermal degradation and hydrolysis failure. The rigid benzene ring structure and high-crystalline polyester polyol system can effectively enhance the thermal stability of the adhesive and improve the high-temperature bonding performance.
The mainstream method for enhancing heat resistance in industry is to optimize the formulation system, select long-chain polyester raw materials, increase the crosslinking density, or introduce rigid functional groups for modification, balancing flexibility and heat resistance. At the same time, reasonable control of the NCO/OH ratio can improve the crosslinking network and reduce molecular breakage in high-temperature and humid environments. In summary, through structural modification and process optimization, the heat resistance of polyurethane laminated adhesive can be significantly improved, meeting the high-temperature usage requirements of high-end flexible packaging.
