Aqueous dispersion adhesives consist of a solid adhesive that is dispersed in an aqueous phase. These adhesives contain water-soluble additives such as surfactants, emulsifiers and protective colloids, which act as a link between the solid adhesive particles and the aqueous phase. They prevent the adhesive particles from sticking together and separating during storage. When drying, these additives evaporate or are absorbed into the adhesive. The adhesive must be completely dry for optimal strength and performance. Small amounts of residual moisture in connection with water-soluble additives weaken the film and reduce its resistance to moisture and water.
Drying of dispersion adhesives
This is particularly important when gluing smooth, non-porous substrates such as metal or plastic. Some water-dispersed adhesives have been formulated with the lowest possible amount of stabilizers in order to increase the initial strength or the final performance of the adhesive. These formulations may require special pumping equipment due to the lower stability of the liquid adhesive. Dried adhesives are no longer dispersible in water, so that wet adhesive formulations can no longer be coated, dried and then activated for bonding with water. Consequently, a substrate must be permeable to water. White glue and carpenter's glue based on vinyl acetate polymers are probably the best-known water-dispersed adhesives. They offer rigid to semi-rigid connection lines and are widely used for bonding wood and wood products, paper, cardboard and corrugated cardboard.
What is the basis of dispersion adhesives?
Water-dispersed adhesives based on natural and synthetic rubber and vinyl acetate copolymers offer flexible connection lines and improved adhesion to plastic, metal, rubber and leather compared to vinyl acetate wood adhesives. Water-based dispersion adhesives can be applied by brush, roller, in beads or by spraying. Cleaning the dried adhesive usually requires the use of organic solvents and sometimes sanding. Follow the manufacturer's instructions for safe handling of the solvent. These adhesives are well suited for the automated assembly of large-area laminates that consist of water-permeable substrates such as film or foil on paper and wood veneer on wood or wood composite.