Paper conservation with an aqueous NaOH/urea cellulose solution

A solution of cellulose dissolved in NaOH/urea was investigated for extending the life of three different model papers. Their mechanical properties such as tensile strength, folding endurance, and tearing strength were tested before and after the treatment. These samples were also characterized by SEM, XRD and FTIR. The results showed that the pre-protection for the papers was absolutely necessary before spraying the cellulose solution on the papers, otherwise the papers would be destroyed in a matter of seconds by the strong alkalinity of the cellulose solution. The pretreatment of impregnating the papers with ethyl acetate in ethanol solution could greatly extend the time that the papers contacted with the cellulose solution to 8 min before water washing. After the treatment, the mechanical properties of the samples improved significantly, especially for their folding endurance, indicating an increase in the interfiber bonds, which improved the flexibility of the papers. The treatment neutralized the acid in the papers and greatly improved the anti-aging properties of the papers, meanwhile the appearance of the paper changed slightly. This study provided a new idea for paper conservation. Graphical abstract