Protonation Process to Enhance the Water Resistance of Transparent and Hazy Paper

Marrying a randomly distributed network of wood fibers with sodium carboxymethyl cellulose (CMC-Na) by impregnation is a scalable method to prepare highly transparent and hazy (TH) paper with superior mechanical properties. However, the poor water resistance of this TH paper is a hindrance for its practical applications. In this study, a facile protonation process along with desalination is proposed to remove the above obstacle by reducing electrostatic repulsion among CMC molecular chains while strengthening the physical cross-linking among CMC molecular chains and also between CMC-H molecular chains and wood fibers in water. Consequently, the protonated TH paper not only presents an enhanced water resistance but also shows a negligible deterioration in optical and mechanical properties compared with the untreated TH paper. Moreover, the influence of the water resistance of various substrates (PET film, untreated TH paper, and protonated TH paper) on the electrical conductivity of inkjet-printed silver nanoparticle lines on them is investigated. We expect that such water resistant, transparent paper with high optical haze may open new avenues for the innovative application of paper and bring added value to existing products.