Barrier Dispersion
Aqueous polymer emulsions applied to paperboard surfaces form continuous protective films that resist moisture and grease penetration. Formulations of water based dispersion coatings rely on acrylic or synthetic latex polymers suspended in liquid media to replace traditional extruded polyethylene barriers. This coating class governs aqueous functional treatments applied by flexographic or gravure coaters on paperboard substrates, ending where solvent-borne or extrusion laminations begin.
Film Formation
Drying involves evaporating the water phase using hot air knives and infrared dryers, which forces suspended polymer particles to coalesce into a dense non-porous layer. Coalescence temperature must be maintained above the glass transition point of the resin to eliminate pinholes and micro-cracks across the surface. Uniform film thickness provides liquid water resistance measured by Cobb test values below ten grams per square metre over eighteen hundred seconds.
Unlike extruded plastic laminates, dispersion layers repulp cleanly in standard mill hydrapulpers, allowing paper fibres to be recovered without specialized separation machinery. Converting lines must monitor coat weight closely, as thin applications leave exposed fibres while thick layers cause blocking inside rewound rolls.
Recyclability Limit
Excessive cross-linking agents impede fibre separation during industrial repulping operations. Pinholes formed during incomplete thermal drying destroy oil barrier performance. Heat-sealing window parameters narrow significantly when surface coat weight exceeds twelve grams per square metre.
