Degradation of handmade paper: Exploration of water adsorption behavior and estimation of lifespan based on time-temperature-humidity superposition

Traditional handmade papers, as the carriers of paper-based cultural relics, inevitably undergo various deteriorations during long-term preservation. Establishing a reasonable degradation kinetic model of handmade paper under the synergistic action of multiple factors is the crucial to evaluate paper aging and lifespan of paper. This study explores the moisture content and diffusion behavior of water molecules in traditional handmade paper to identify the interaction between fibers and water molecules at the accessible sites by two-dimensional infrared spectroscopy (2D-COS). Additionally, the optimized second-order kinetic models for the degradation of three types of Kaihua handmade papers was presented based on the time-temperature-humidity superposition method. A time-temperature-humidity translation factor is incorporated into the dynamic model to quantitatively analyze the synergistic effect of temperature and humidity on the degradation rate of handmade paper. The degradation rates of handmade paper with different raw materials and handcraft processes demonstrated significant effects of the cooking and bleaching processes on the aging degradation process and the durability of the paper. The improved second-order degradation kinetic model, considering the cooperation process with multi-factors and mechanisms, enables the extrapolation of paper aging properties at arbitrary temperature and humidity effectively, which provides a more reasonable estimation of handmade paper's lifespan.