Effects Of UV Irradiationon The Structure And Properities Of Collagen Matrix

In the present study, the pickled goat skins were tanned by different chemicals including chrome tanning agent, glutaraldehyde tanning agent, and quebracho extract, respectively. The wet blues were fatliquored by paraffin fatliquoring agent, granulesten fatliquoring agent, and sulphitated granulesten fatliquoring agent, respectively. The samples were treated with UV irradiation (wavelength 312nm) for different time intervals. The mechanical properties, thermal stability, thermal degradation behaviour, water vapor permeability, dimensional stability, and morphology of goatskin collagen matrices before and after UV irradiation were investigated. The influence of UV irradiation on the molecular structure of collagen was studied by infrared spectra.The dry heat shrinkage behaviors of the collagen fibers were performed by using the thermal platform microscopy. It was shown that UV irradiation affects the dry heat shrinkage behaviors obviously. The dry heat shrinkage temperature (Ts) of native, tanned and fatliquored collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). Increasing UV irradiation time leads to a decrease in shrinkage ratio. For the same irradiation time, the UV irradiation exerted more dramatic effect on the un-tanned collagen matrix, compared with the tanned and fatliquored ones. The dry heat shrinkage temperature showed that quebracho extract tanned goatskin collagen fibers have better stability against UV irradiation than native and other tanning agents treated goatskin collagen fibers. Un-fatliquored samples have better stability against UV irradiation than the fatliquored one.The thermal degradation behaviors of native, tanned and fatliquored before and after UV irradiation collagen fibers were investigated as well. The thermal degradation behaviors of samples were characterized by using thermo-gravimetric thermal analyzer (TG), and both methods of Coats-Redfern and Horowitz-Metzge were applied to calculate the thermal degradation activation energy of the samples. The results showed that the thermal degradation activation energy of native collagen fibers increases at the first few hours of UV irradiation (0-4h) and decreases after irradiation for longer time (8-64 h). The thermal degradation activation energy of tanned and fatliquored collagen fibers decreases after long time of UV irradiation.The mechanical properties of goatskin leathers before and after UV irradiation were investigated. It was found that the tensile strength of the goatskin matrices increases slightly in the first few hours of irradiation (0-4 h), and decreases dramatically after longer time (8-64 h) of UV irradiation. Increasing UV irradiation time leads to a decrease in elongation at break and tensile fracture energy. The water vapor transmission rate decreases at the first few hours of UV irradiation (0-4 h) and increases after irradiation for longer time (8-64 h). UV irradiation results in a continuous decrease in sample dimension.Scanning electron microscopy observation suggested that UV irradiation induces crack and loss of skin tone. ATR-IR spectra of goatskin collagen showed that after UV irradiation, the positions of Amide A and Amideâ…¡bands were shifted to lower wavenumbers. There was not any significant alteration in the position of Amide I bands of collagen after UV irradiation. It was indicated that phototransformation occurred during UV irradiation and changed the conformational state of collagen.