POTENTIAL OF VEGETABLE TANNING MATERIALS AND BASIC ALUMINUM SULPHATE IN SUDANESE LEATHER INDUSTRY (PART II)

Abstract

Ecological pressures on chromium have now forced the leather industry to look for possible alternatives. A vegetable-aluminum combination tannage has been studied, with special attention being given to the intended final product. Aluminum is a mineral tanning agent that is widely used in the leather industry to stabilize collagens. In this study, stabilization of skin collagen by crosslinking vegetable agent and aluminum has been explored. This kind of chrome-free tannage gives us leathers with a shrinkage temperature around 125 o C, elongation at break 65.6%, tensile strength of 38 N/mm 2 , and tear strength of 98 N/mm. The chemical properties of the combination tanned leathers offer a product with reduced water solubility and comparable free fats and oil content. A vegetable pre-tanning followed by basic aluminum sulphate retanning was found to produce stronger leather with durable characteristics. In contrast, pre-tanning with aluminum sulphate possibly tightens the collagen fiber network, preventing high molecular weight vegetable tannins from interacting with collagen fibres. Optimal results were obtained when 20%(w/w) vegetable tannin from Acacia nilotica pods (garad in the local language) and 5% aluminum sulphate were used.