Chemical Composition
Emulsion coatings formulated with suspended polymer spheres provide a non-solvent method for applying protective and barrier layers to paperboard substrates. An acrylic aqueous dispersion is applied during the converting stage to block water vapour and grease migration. Low viscosity allows the liquid to spread evenly across the moving paper web before the moisture evaporates.
Film Formation
Water removal through thermal drying forces the suspended polymer particles to coalesce into a solid, hydrophobic barrier. Acrylic aqueous dispersion relies on controlled evaporation rates to avoid skinning, where a dry crust forms over trapped moisture and creates pinholes. When dried correctly, the polymer chains interlock to form a highly flexible, clear film that resists chemical penetration.
Converting Performance
Barrier boards processed with these coatings must survive high-speed folding and creasing without developing hairline fractures. While rigid waxes may fracture under mechanical stress, the acrylic aqueous dispersion forms an elastomeric layer that flexes with the cellulose fibres. The resulting barrier resists liquid penetration even at ninety-degree folds, ensuring that food service boxes do not leak at the corners or lose structural strength when filled with hot food.
This mechanical flexibility is tested by applying dyed oil mixtures to the creases and monitoring for migration.
