The properties of the basic materials used in the technological process, in particular the laminating adhesives for polymer films, have a decisive influence on the operating characteristics of the finished laminate. The knowledge about the range of adhesives, as well as the specifics of systems for their application, is an important basis for further improvement of the technology and the study of immediate practical properties.
The adhesive bonding of films occurs mainly under the influence of intermolecular interaction forces in the boundary layer between the substrate and the adhesive, and its strength depends on the nature and the number of functional groups, the structure of materials, and the interphase surface energy. Due to the wide variety of properties of adhesives, one can create materials that have brand new, often unexpected, but sometimes predictable functional parameters and characteristics.
In the films laminating process, as a rule, there is a change in the aggregate state of the adhesive from a liquid (which provides better contact between the adhesive and substrate) to solid. This greatly increases the viscosity and the melting point of the adhesive. Obviously, the hardener of adhesives that contain and do not contain solvents will be different.
In the first case, the solid phase in the adhesive layer appears due to the evaporation of the solvent or dispersion medium and an increase in the concentration of the main component - a film-forming agent. In the other case, the adhesive hardening is due to chemical reactions leading to a multiple increase in the molecular weight of the main component of the adhesive composition in the chemical process, in its polymerization and crosslinking process.
