Effects of Accelerated Ageing on the Physical and Chemical Properties of Chrome-free Leather

With the expansion of market demand for chrome-free leathers, much attention has been paid to the safety in using them. Four kinds of chrome-free upper leathers made by Vegetable-Glutaraldehyde (Veg-GA), Glutaraldehyde-Vegetable (GA-Veg), Vegetable-Aluminium (Veg-Al) and a synthetic agent were subjected to accelerated ageing by hot air, UV light and Xe lamp respectively for 96 hours. The physical qualities and chemical indicators of these leathers before and after ageing, such as the shrinkage temperature (Ts), tensile strength, tear strength, colour difference, water vapour permeability, formaldehyde, phenol and aniline were tested. It was shown that some common rules apply to the four kinds of chrome-free upper leather samples after ageing, Xe-lamp ageing has made the tear strength, formaldehyde and phenol levels reduce the most and the aniline level increased the most. UV-light ageing has caused the maximum colour difference change whilst hot-air ageing has caused the maximum Ts decrease. All of the ageing methods have enhanced the water vapour permeability. Summarising, leather samples made differently have different physical quality indicators after the same ageing treatment. As the basis of the leather quality change, it is found that the leather fibre turns into a bundle, curled, loose and distorted no matter what kind of ageing treatment is used.