The principle and improvement methods of aging resistance of flexible packaging polyurethane laminating adhesive

The aging resistance of the flexible packaging polyurethane laminating adhesive directly determines the long-term storage stability of the composite packaging. During the storage, transportation and end-use processes of flexible packaging, it will continuously be exposed to light, high temperature, oxygen, moisture and oil erosion. If the adhesive has insufficient aging resistance, problems such as yellowing, delamination, blistering, and attenuation of peel strength due to aging failure are likely to occur. 

 

The aging of Polyurethane Adhesive essentially involves the degradation of molecular chains and oxidative breakage. In a common polyurethane system, ester bonds and amide bonds are subject to long-term exposure to ultraviolet rays and thermal oxidation, resulting in chain segment breakage, a decrease in crosslink density, and gradual brittleness and softening of the adhesive layer. At the same time, hydrolytic aging gradually damages the bonding interface, significantly reducing the bonding force between the film and the aluminum foil, leading to premature failure of the packaging. 

Highly resistant to aging polyurethane adhesives mostly adopt modified weather-resistant formulations. By introducing hydrolysis-resistant and ultraviolet-resistant molecular structures, they enhance the antioxidant and anti-hydrolysis capabilities of the adhesive layer, effectively slowing down the aging rate of the adhesive layer. These adhesives are particularly suitable for scenarios such as long-term storage of leisure foods, outer membranes of daily chemicals, and outdoor light-avoidance packaging.

 

The production end can also improve the aging resistance performance through process optimization. By strictly controlling the uniformity of coating amount, ensuring adequate curing and cross-linking, reducing workshop humidity and residual moisture, and minimizing post-hydrolysis risks, the adhesives can significantly extend the service life of flexible packaging and improve the stability of product shelf life quality. The stable cross-linking structure combined with high-quality weather-resistant formulations can significantly prolong the service life of flexible packaging and enhance the stability of product shelf life quality.