Effect of Syntan to Fatliquor Ratio on Porosity and Mechanical Properties of Wet-blue Leather

Different types of leathers with varied end applications can be made from same raw material. Post-tanning is the operation, which imparts the functional properties required for the final leather. The amount of post-tanning auxiliaries such as syntan (S) and fatliquor (F) used in the leather making, make it possible to convert the same animal skin into various leather types. In this work, the sheep wet-blue has been converted into garment (S:F 1:2) and upper (S:F 2:1) leather by varying the S to F ratio. Here, an attempt has been made to study the influence of S to F ratio on the porosity and mechanical properties of garment/upper leather with respect to sheep wet-blue as a control. Thermoporometry results show that the reduction in pore distribution of garment leather with respect to wet-blue leather is about 62.3% and that of upper leather is 83%. Capillary flow porometry results show that the maximum distribution of through pore throat diameter of upper leather is found to be shifted towards 0.1-0.2 mu m from 0.3-0.5 mu m (wet-blue leather), whereas in the case of garment leather pores are uniformly distributed in the range of 0.1-0.5 mu m. The influence of post tanning auxiliaries on air permeability reduction is higher for upper leather (83%) than garment leather (41%). Morphological analysis using SEM shows that loosely packed arrangement of wet-blue leather becomes cemented fiber structure in case of upper leather and uniform fine fiber splitting has been observed for garment leather. Tensile strength of wet-blue leather is decreased by about 23% when it is converted into upper leather and that of garment leather is increased to about 16%.