Novel Vegetable Tanning Techniques by Notholithocarpus densiflorus Extract and Fatliquoring with Indigenous Bovine Fat

The major technical challenge of vegetable tanning is to improve the higher wear-comfort, leather strength and water resistance efficiency in daily necessities of leather products, aiming as an alternative to chrome tanning. The demonstration has been made by indigenous bovine fat and Tanoak tree (Notholithocarpus densiflorus) bark-wood extract for usage in the tanning process as a new kind of stuffing tanning technique for the first time. The tannin content maximum efficiency was found at 34.25% for the bark and 28.5% for the wood sample. The presence of tanning content was characterized by using UV-visible absorption spectroscopy, FTIR spectroscopy and HPLC techniques. The characterization data revealed mainly catechol presence in the bark and pyrogallol presence in the wood. The stuffing techniques tanned leather showed a shrinkage temperature of 95±2 °C. Other physical properties such as tensile strength, tear strength, grain cracking load, and flexing endurance were comparable to conventional chrome-tanned leather. The cross-sectional morphology and thermal degradation of the tanned leathers were characterized by FE-SEM and TGA techniques which revealed a fat-coated compact structure of the leather fibres and decomposition at mainly 100 °C to 300 °C respectively. The average contact angle of a water droplet on bark-tanned leather was greater than 100° and wood-tanned 88° at the solid-liquid interface respectively, which indicated the low wettability of leather as a water resistance leather. These new kinds of stuffing techniques of vegetable tanning processes will help to replace the chromium tanning, sustainable tanning approach and save the environment.