Modifications of paper and paperboard surfaces with a nanostructured polymer coating

Organic nanoparticles synthesized by imidization of styrene-maleic anhydride copolymers are deposited as a top-coating onto paper and paperboard substrates from a stable aqueous dispersion with maximum solid content of 35 wt.%. The morphology, physical characteristics and chemical surface properties of the coatings are discussed in this paper, using scanning electron microscopy, atomic force microscopy, contact angle measurements and Raman spectroscopy. Due to the high glass transition temperature of the polymer nanoparticles, a unique micro- to nanoscale structured coating is formed that favourably improves the gloss, printing properties (ink-jet printing test and off-set printing test), surface hydrophobicity (maximum water contact angle 140°) and water repellence (reduction of Cobb-values). The interaction of the nanoparticle coatings with the cellulosic paper web results in improvement of the mechanical paper strength and is attributed to hydrogen-bonding between the nanoparticles and the cellulosic fibers.