Vaterite-type calcium carbonate and aminopropyltriethoxysilane-modified cellulose nanofibrils for preservation of aged paper

Abstract

Deacidification and structural reinforcement are critically important for the long-term preservation of paper cultural relics. In this study, a novel approach is presented to synergistically combine highly reactive vaterite-type calcium carbonate with aminopropyltriethoxysilane-modified cellulose nanofibrils (NH2-CNFs) for the restoration of aged paper. Employed as a deacidification agent, vaterite demonstrated superior efficacy at a low dosage in comparison with commercially available calcite-type calcium carbonate. Concurrently, the carboxylate content of NH2-CNFs was reduced, enhancing its hydrophobicity and thermal stability. A comprehensive characterization of both vaterite and NH2-CNFs was conducted using multiple analytical techniques. Upon application of this restoration system to aged paper samples, the pH and alkaline reserve were elevated to 8.05 and 0.637 mol/kg, respectively. The tensile strength of the paper sample was augmented by 15 %, while folding endurance and tearing resistance were enhanced by 139 % and 66 %, respectively. Notably, the integration of vaterite exhibited no deleterious impact on the mechanical properties of the paper substrate. Additionally, this treatment imparted a substantial anti-aging effect, as evidenced by the results of dry heat and UV-irradiation aging. Consequently, this research introduces a novel and efficacious methodology for the restoration of aged paper, offering promising implications for the conservation of historical documents.