Zhu Zirui, Zhang Kai, Xue Yu, Liu Zhongming, Wang Yujie, Zhang Yanli, Liu Peng, Ji Xingxiang
State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan 250353, China.
Institute for Preservation and Conservation of Chinese Ancient Books, Fudan University Library, Fudan University, Shanghai 200433, China.
Molecules. 2024 Dec 5;29(23):5741. doi: 10.3390/molecules29235741.
Handmade papers, as carriers of paper-based cultural relics, have played a crucial role in the development of human culture, knowledge, and civilization. Understanding the intricate relationship between the structural properties and degradation mechanisms of handmade papers is essential for the conservation of historical documents. In this work, an artificial dry-heat-accelerated aging method was used to investigate the interplay among the mechanical properties of paper, the degree of polymerization (DP) of cellulose, the chemical composition, the hydrogen bond strength, the crystallinity, and the degree of hornification for paper fibers. The results demonstrated for the first time that the mechanical properties of handmade bamboo paper exhibited an initial plateau region, a rapid decline region, and sometimes a second plateau region as it undergoes a dry-heat aging process. The changes in cellulose, hemicellulose, and lignin content were tracked throughout these three stages. The lignin content was relatively stable, while the cellulose and hemicellulose content decreased, which was consistent with the observed decline in mechanical properties. When the DP of cellulose decreased to the range of 600-400, there was a critical point in the mechanical properties of the paper, marking a transition from the initial stable region to a rapid decline region. The fiber embrittlement caused by cellulose chain breakage resulting from the decrease in DP was counteracted by the enhancement of intermolecular hydrogen bonds and the hornification process. A second stable region appeared when the DP was less than 400, marking a transition from a balanced or slightly decreasing trend in the initial plateau region to a sharp decline. This study also discussed for the first time that the formation of the second plateau region may be due to the presence of hemicellulose and lignin, which hinder the further aggregation of cellulose and maintain the structural stability of the fiber cell. The findings of this study can provide guidance for improving ancient book preservation strategies. On the one hand, understanding how these components affect the durability of paper can help us better predict and slow down the aging of ancient books. On the other hand, specific chemical treatment methods can be designed to stabilize these components and reduce their degradation rate under adverse environmental conditions.
手工纸作为纸质文物的载体，在人类文化、知识和文明的发展中发挥了至关重要的作用。了解手工纸的结构特性与降解机制之间的复杂关系对于历史文献的保护至关重要。在这项工作中，采用人工干热加速老化方法来研究纸张的机械性能、纤维素的聚合度（DP）、化学成分、氢键强度、结晶度以及纸纤维的角质化程度之间的相互作用。结果首次表明，手工竹纸在经历干热老化过程时，其机械性能呈现出一个初始平稳区域、一个快速下降区域，有时还会出现第二个平稳区域。在这三个阶段中，对纤维素、半纤维素和木质素含量的变化进行了跟踪。木质素含量相对稳定，而纤维素和半纤维素含量下降，这与观察到的机械性能下降一致。当纤维素的DP降至600 - 400范围内时，纸张的机械性能出现一个临界点，标志着从初始稳定区域向快速下降区域的转变。由DP降低导致的纤维素链断裂引起的纤维脆化被分子间氢键的增强和角质化过程所抵消。当DP小于400时出现第二个稳定区域，标志着从初始平稳区域的平衡或略有下降趋势向急剧下降的转变。本研究还首次讨论了第二个平稳区域的形成可能是由于半纤维素和木质素的存在，它们阻碍了纤维素的进一步聚集并维持了纤维细胞的结构稳定性。本研究的结果可为改进古籍保护策略提供指导。一方面，了解这些成分如何影响纸张的耐久性有助于我们更好地预测和减缓古籍的老化。另一方面，可以设计特定的化学处理方法来稳定这些成分并降低它们在不利环境条件下的降解速率。
