Synthetic Polymer
Aqueous emulsions of styrene butadiene provide the primary adhesive force in paper coatings through the formation of a cross-linked film. The polymer chains contribute to the mechanical integrity of the coated layer by bridging the gap between pigment particles and the underlying cellulose matrix. Binder concentration dictates the surface strength of the sheet during the final printing operation.
Coatings formulated with this resin maintain high gloss levels and provide resistance to water penetration.
Application Property
Elasticity inside the dried coating layer depends on the relative ratio of the two monomers. Increased levels of butadiene soften the film to improve foldability while higher styrene content promotes hardness and ink receptivity. Mill operators monitor this ratio to adjust the resistance of the substrate to linting or picking when subjected to high speed mechanical stresses.
Manufacturers add small amounts of stabilisers to preserve the emulsion shelf life before the material enters the mixing stage. Heat exposure during the drying cycle initiates film formation which anchors the pigment pigments securely to the fibrous surface.
Production Boundary
Coating formulation requires precise control of pH and viscosity to ensure stable flow through the metering systems of the paper machine. Excess quantities of the dispersion within the slurry reduce the porosity of the final sheet which hinders ink drying speeds and causes smearing. Deviations in the polymer particle size distribution affect the opacity and light scattering characteristics of the finished product.
Proper storage prevents phase separation and the accumulation of coagulated material that would damage the blade edge of the coater. Synthetic binders dominate the modern packaging industry because the material retains structural consistency across varied environmental humidity conditions.
