Analysis of the Heat Resistance of Polyurethane Adhesives for Flexible Packaging
2026,02,03
The polyurethane adhesives used for flexible packaging have certain heat resistance, but their heat resistance capacity is not fixed. It needs to be judged comprehensively based on the formulation design, processing technology and application scenarios. Whether the core can meet the requirements depends on the temperature conditions and performance requirements in the specific application.
From the perspective of basic performance, the molecular structure of this type of adhesive contains amide ester bonds, ether bonds or ester bonds, etc. Through reasonable regulation, it can achieve good thermal stability. The conventional products can withstand a temperature range of -40℃ to 120℃ and can be adapted to common high-temperature compounding and low-temperature refrigeration scenarios in soft packaging. It can maintain stable adhesion at a compounding roller temperature of 50℃ to 80℃, and the environment at 40℃ to 55℃ during the curing process will not affect its final bonding strength.
For special requirements, the heat resistance of the modified products can be significantly enhanced. For example, the adhesive for heat-resistant flexible packaging can withstand high-temperature sterilization processes of 121℃ for 30 minutes or 135℃ for 30 minutes, meeting the requirements for high-temperature sterilization in food packaging. The core of the heat resistance improvement lies in optimizing the molecular structure, such as introducing rigid groups like aromatic rings and oxazolidones to increase the crosslinking density, or through nano-composite modification to enhance thermal stability. After treatment, the long-term operating temperature can exceed 150℃, and it can withstand temperatures above 200℃ for a short period.
It should be noted that the heat resistance is influenced by multiple factors. Incomplete curing can lead to easy peeling and delamination at high temperatures, so the curing temperature and time must be strictly controlled; an excessively high proportion of ester bonds in the molecular chain will reduce the heat resistance, while the ether bond structure is more conducive to enhancing the high-temperature stability. In practical applications, products with matching heat resistance grades need to be selected based on whether the soft packaging is exposed to high temperatures and the type of medium, in order to ensure the reliability of the bonding.
