Analysis of the Flash Point of Flexible Packaging Polyurethane Laminating Adhesive

Flash point is the core safety indicator for evaluating the flammable and explosive characteristics of flexible packaging polyurethane laminating adhesive. It is also an important basis for safety control during the production, storage, and coating application of the adhesive. It directly affects the safety production norms of the flexible packaging composite production line. The industry measures the flash point of adhesives according to the GB/T 30777 closed cup method, and in combination with the HG/T 5376-2018 industry standard, clearly defines the flash point properties of different types of polyurethane laminating adhesives. 

 

The commonly used polyurethane laminating adhesives for flexible packaging are mainly divided into solvent-based and solvent-free types. The flash points of these two types vary significantly. The mainstream ester-soluble and alcohol-soluble solvent-based polyurethane laminating adhesives contain volatile solvents such as ethyl acetate, and their flash points are generally ≤ 28℃. They belong to Class A hazardous chemicals and have extremely high risks of combustion and explosion. Some products containing special solvents have flash points as low as -4℃. At room temperature, they easily volatilize to form flammable vapors, which can ignite and explode upon contact with fire or static electricity. However, solvent-free polyurethane adhesives do not contain volatile solvents, resulting in a significant increase in flash point and better safety and stability. 

The flash point value directly determines the hazard level and usage specifications of the adhesive. For low-flash-point solvent-based adhesives, the environmental temperature must be strictly controlled throughout the process. Open flame operations are strictly prohibited. At the same time, good ventilation and static electricity elimination measures should be taken in the workshop. The storage area should be divided into a separate section for Class A hazardous materials. Construction equipment should be equipped with explosion-proof devices. In lamination production scenarios such as flexible packaging food and daily chemicals, accurately controlling the flash point indicators and strictly implementing graded safety management is the key to avoiding safety hazards and ensuring the orderly and compliant production.