Animal skin,as a natural polymer material with abundant sources,was used to make various leather items in early human society.Ancient books,archives,and other cultural relics made from them carry profound cultural value.Studying the internal structure of them can provide good theoretical support for the protection and inheritance of cultural relics^[1].For example,artifacts such as parchment and Chinese shadow puppets that have not been tanned with tanning agents are called untanned hide artifacts.This system combined traditional production methods and modern processing techniques to study the performance changes of untanned hide during the production process.

The research method for untanned hide referred to IDAP(Improved Damage Assesment of Parchment)^[2],and quantitative and qualitative measurement methods such as SEM and FTIR^[3] were used to measure the effects of different pretreatment methods and chemical reagents on material properties.

The treatment methods for the samples in this study include saponification or emulsification reactions for defatting the raw skin,and adding different depilatory reagents, including alkaline reagents such as sodium sulfide or gastric protease,to the pretreated samples.

The analysis of infrared spectra in the study can reveal the effects of different chemical reagents on the peak shift of untanned Pete's characteristic,and SEM scanning can observe the changes in its intrinsic fiber configuration.The wet heat shrinkage temperature and stress-strain curve reflect the changes in its mechanical properties.

Plant-based enzymatic extraction of collagen from tannery rawhide trimmings can play an important role in the utilization of tannery solid waste. This study employed ficin enzyme derived from fig leaves waste for collagen extraction and compared the procedure with conventional acetic acid extraction. Response surface methodology (RSM) analysis revealed that ficin enzyme-soluble collagen (FSC) yielded 15.28% at a hydrolysis time of 39.27h, a ficin enzyme dose of 5.54%, and a mixing ratio of 15.87. In contrast, a lower yield of 9.27% was observed in the case of acetic acid-soluble collagen (ASC) at a hydrolysis time of 46.44h, a acidic acid concentration of 1.30mol/L, and a mixing ratio of 19.41. Fourier transform infrared spectroscopy (FTIR) confirmed the successful extraction of both ASC and FSC. Thermogravimetric analysis (TGA) indicated the higher thermal stability of ASC compared to FSC. The SEM images showed the presence of an organized porous-like structure in ASC and a separated irregular sheet-like mesh in FSC. After sonication treatment, there denoted the presence of a disorganized porous-like structure in UASC and a gathered irregular sheet-like mesh linked to each other in UFSC. Based on the negative ellipticity values, it can conclusion that PSC showed less integrity of triple helical structure while FSC exhibited well integrity of triple helical structure that comparable of standard collagen samples. Moreover, the present research confirmed that an ultrasound treatment at 140W for 30 min did not significantly disturb the triple helical structure of collagen. Notably, FSC and UFSC, with comparable UV absorption, seemed to be less proteinaceous impurity than other collagens with different extraction conditions. Hence, the results confirmed that appropriate sonication treatment would not cause contamination of non-collagenous proteins.