Abstract

As a novel, mild, environmentally friendly and efficient thermal technology, microwave is freely used in many fields. Hence, an attempt has been made to apply the microwave in vegetable tanning to accelerate tanning reaction and improve the performance of the leather. In this work, the bonding properties of tannin extracts under microwave irradiation heating (MIH) were investigated compared with water bath heating (WBH). Thermal performance of the leather treated under MIH was characterized by the shrinkage temperature and differential scanning calorimeter. The composition and properties of tanning liquors were analyzed by ultraviolet-visible absorption spectroscopy, high performance liquid chromatography and gel permeation chromatography. The results showed that the thermal stability of leather was improved and the shrinkage temperature of the leather increased about 1°C under MIH. Compared with a conventional tanning, the composition and properties of the liquids changed under MIH, for example, the content of macromolecules and total phenolics content reduced. Furthermore, the number-average molecular weight of tanning liquid also decreased. The results indicated that MIH could promote the penetration of tannin extracts and combination between tannins and collagen.