Analysis of Bonding Strength of Different Flexible Packaging Polyurethane Laminated Adhesives

Polyurethane laminating adhesive is the core material of flexible packaging composite processing, and its bonding strength directly determines the bonding stability, weatherability and safety of composite film. Different types of polyurethane laminating adhesives have different formulations and process characteristics, and the adhesive strength performance is significantly different, which is suitable for different production and use scenarios of flexible packaging.

 

 

Dry-cured Polyurethane Adhesive has the best overall bonding strength. This kind of adhesive has sufficient adhesive amount and uniform adhesive layer thickness. After curing, it can slightly swell the ink layer, enhance the bonding force between the film and the ink and adhesive layer, and has high normal peeling strength. It is suitable for high-strength bonding scenes such as aluminum-plastic composite and high-barrier film, and is not easy to delaminate.

 

Solvent-free polyurethane adhesive is environment-friendly and residue-free, which is suitable for food flexible packaging, and its bonding strength is greatly affected by the formula ratio. When the mass fraction of isocyanate group is 17%, the cross-linking structure of adhesive layer is the most stable, and the adhesive strength reaches the peak. The products prepared by modified polyester polyol can still maintain stable peel strength after boiling water, and have excellent wet and heat resistance.

 

Waterborne polyurethane adhesive has the advantage of environmental protection and safety, and its bonding strength is closely related to the crystallinity of resin. When the crystallinity is moderate, its bonding performance is the best, but its water resistance and temperature resistance are weak, and its bonding strength is easy to decay in wet environment, so it is only suitable for ordinary light flexible packaging. On the whole, in actual production, it is necessary to optimize the adhesive according to the packaging substrate and the use environment to ensure the bonding stability.