Investigation into the deterioration process of archaeological bamboo strips of China from four different periods by chemical and anatomical analysis

The chemical and the anatomical features of the archeological bamboo strips of China from four different periods were compared with the non-degraded fresh bamboo to understand the deterioration process. Unprocessed bamboo strips, isolated hemicelluloses and lignin fractions were analyzed with wet chemical analysis, GC, FTIR, UV and XRD to investigate the chemical degradation. It was found that the crystalline cellulose and the polyxylose degraded with increasing age, leaving the amorphous cellulose and the lignin with syringyl moieties modified as the main residual cell wall materials. Serious degradation of p-coumaric acid and ferulic acid were detected and indicated the cleavage of the linkage between the lignin and the carbohydrate, which might facilitate the degradation of carbohydrate. The anatomical analysis with SEM and TEM revealed the vanishing of the parenchymatous ground tissue and vessels and the cellulose microfibrils in the multilayered secondary wall. The differences in lignin content and in tissue density (cell thickness/cell size) between the parenchyma cells and the sclerenchymatous fiber cells fundamentally led to the formation of the unique anatomical structure of the archeological bamboo strips which was composed of parallel solid bundles. The effects of the chemical and the anatomical degradation on the mechanical properties were also discussed.