Polymeric Binder
Chemical-reactive gluing systems consisting of a base resin and a curing agent or hardener provide the highest levels of thermal and chemical resistance for high-performance laminating. A two-component adhesive requires the precise mixing of an isocyanate-functional hardener with a hydroxyl-terminated polyol base resin before application. Once mixed, the two components undergo a crosslinking reaction to form a three-dimensional polymer network.
This system is the preferred choice for demanding packaging applications like hot-fill pouches, foil-to-board lamination, and retortable liquid cartons.
Cure Profile
Time and temperature required for the mixed adhesive to reach its full mechanical and chemical properties depend heavily on the catalyst and reactive group concentration. During the curing phase, the mixed liquid moves from its open-time window through a gel point to a solid, fully crosslinked state. If the ratio of the two components is incorrect, the adhesive will remain under-cured, resulting in sticky film layers, low peel strength, and high residual monomer migration.
Monitoring the mixing ratio on the lamination line is essential.
Processing Window
The reaction begins immediately upon mixing, limiting the usable lifetime or pot life of the adhesive in the applicator pan. Converters must schedule runs to avoid gelation in the coating system, which can cause severe machine downtime and roller damage.
