Effect of the surface treatment with CNF/oxidized starch on the physical properties and the printability of paper

This study was carried out to investigate the effect of the surface treatment with CNF alone and/or CNF-oxidized starch mixtures on the physical properties and printability of paper. CNF has better fluidity than the oxidized starch during coating process, and its coverage was excellent even though the small amount was applied to paper surface. The surface roughness was somewhat reduced by the formation of thin film. The bulk of the paper showed no significant change when applied in small amounts of CNF and/or oxidized starch mixtures, but decreased as the application amount exceeded 5 g/m2. The air resistance of paper was 853 seconds when it was applied with CNF only 2.35 g/m2, and it was impossible to measure the air permeability regardless of the application amount when the mixtures of oxidized starch were applied on the paper surface. The tensile strength, tear strength, bending strength and folding endurance, as well as elongation, were improved by surface treatment with CNF and/or the mixtures of CNF and oxidized starch. The dry pick strength of the surface treated paper showed the lowest value in the CNF treatment, and it was improved with the increase of oxidized starch content. The wet pick strength was poor enough to be unmeasurable until CNF was applied by 2 times, and excellent results were obtained as the amount of oxidized starch added increased.