Thermal resistance of organic nanoparticle coatings for hydrophobicity and water repellence of paper substrates

The modification of paper substrates by organic nanoparticle coatings offers an attractive alternative for creating hydrophobic and water-repellent surfaces without fluorinated chemicals. The nanoparticles were synthesized by imidization of poly(styrene-maleic anhydride) and applied to a standard paper grade by means of a laboratory bar-coating process. The effects of supplementary heat treatments of the coated papers were investigated in terms of coating morphology and hydrophobicity: a unique coating structure is formed with a combination of microdomains that are internally structured at the nanoscale. The relatively high glass transition temperature of the nanoparticles allows for good thermal stability of the coating with almost no morphological changes at heating up to 180°C. The changes in chemical composition were investigated by diffuse reflectance infrared spectroscopy (DRIFT) and UV/VIS spectroscopy. The latter techniques qualitatively describe the effects of thermal treatments on the imide and styrene moieties. Contact angle measurements indicate that there is an optimum curing temperature in order to obtain a maximum advancing contact angle of 133° to 150°.