Effect of UV Irradiation on Vegetable Tanned Leather

This article aims at studying the influence of UV irradiation on vegetable tanned leather. Vegetable tanned leather was treated in QUV chamber (T = 50°C, irradiance = 1.77 W/mm2nm, λUVA = 340 nm) for 0, 30, 60, 90, 120 and 150 hours. Then, these samples were evaluated by different analytical methods to get a whole picture of the leather during the irradiation. Micro hot table (MHT), differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to evaluate the influences of UV irradiation on thermal behaviors. Damages to mechanical properties were also analyzed by a standard method. Fourier transform infrared spectroscopy (FT-IR) and optical microscopy were used to investigate the changes of structural and histological properties during aging process. With the extension of aging time, thermal stability was gradually reduced to lower values, including shrinkage temperature, thermal denaturation temperature, associated enthalpy and temperature for maximum decomposition rate. In addition, mechanical properties such as tensile strength, tear strength and elongation at break also gradually decreased. The FT-IR results showed that, during the aging process, amide I and amide II band of the tanned collagen gradually shifted to lower numbers, indicating an increasingly serious damage to the structure of the peptide chain, that corresponds to obvious fibril breakages which are also detected through optical microscopy.