Stabilization of the Tensile Strength of Aged Cellulose Paper by Cholinium-Amino Acid Ionic Liquid Treatment

In this study, a chemical stabilization method, that preserves the tensile strength of artificially aged paper pretreated with an aqueous solution of ionic liquid, is presented. Pure cotton cellulose paper samples were soaked with cholinium glycinate ionic-liquid solution either before or after the artificial aging process, which was based on thermal degradation in dry air. The tensile strength of artificially aged paper was measured by using the double-folding technique. The role of ionic liquids was investigated by mid-infrared and terahertz time-domain absorption spectroscopy. It was found that the tensile strength of pretreated samples is higher than that of other aged samples. A model for changes in the cellulose structure caused by oxidation and by the binding of ionic liquid molecules is proposed, based on the analysis of the mid-infrared absorption bands in the carbonyl/carboxyl region at 1590-1750 cm-1. Terahertz spectroscopy data indicate that the ionic liquid molecules penetrate in the larger size porosity, acting as binders among cellulose fibers to maintain the tensile strength of paper. © 2016 American Chemical Society.