Surface Energy Measurement Methods for Polyolefin Packaging Films
Polyolefin surface energy audits require OWRK polar component tracking and dyne fluid validation to prevent lamination delamination and slip agent masking.
Solventless Laminating Adhesives
Polymer Bonding
Two part polymer systems that join flexible packaging webs without organic solvents eliminate the need for drying tunnels. The application of solventless laminating adhesives relies on a chemical reaction between an isocyanate and a polyol to form a strong polyurethane bond. These adhesive components are mixed in a precise ratio immediately before application to the moving film web.
Because there is no solvent to evaporate, this process is energy-efficient and eliminates emissions of volatile organic compounds.
Curing Mechanism
Chemical cross-linking occurs over several days at controlled temperatures to reach full bond strength. The mixed adhesive has a low initial viscosity, allowing it to be applied as a very thin, uniform layer on the film. After application, the two webs are pressed together in a nip, and the laminate is stored in a heated room to accelerate the chemical reaction.
This curing time must be managed carefully to ensure the packaging is safe for food contact.
Safety Considerations
Incomplete curing can leave unreacted monomeric isocyanates that migrate through the film into the food. These primary aromatic amines pose a health risk, so converters must verify that curing is complete before the laminate is used. Monitoring the storage temperature and duration ensures that the adhesive achieves full cross-linking.