Effect of crusting operations on the mechanical properties of leather

Physical properties of leather form vital quality parameters that determine the performance characteristics in their areas of applications. However, the transformational processing of hide to leather involves a series of both chemical and physical/mechanical changes that affect these mechanical properties. Many researches have been published regarding the effect of processing on the mechanical properties of leather. However, the effect of entire crusting operations (post tanning) on the mechanical properties strength is not documented. This study reports the findings of the effect of crusting operations (retanning, dyeing and fatliquoring) on the mechanical properties of the final leather. Results have shown that retanning process improves tear and tensile strengths, distensions at crack and burst, and shrinkage temperature. An improvement in the organoleptic properties such as fullness was recorded in retanned crust leather. However, the uniformity coefficient and percentage elongation significantly decreased after retanning. Dyeing raises the elongation at break, distensions at crack and burst, shrinkage temperature and uniformity coefficient whereas both tensile and tear strengths decreased after dyeing. Similarly, fatliquored samples recorded higher elongation at break values, and distension values. Conversely, tensile and tear strengths, shrinkage temperature and uniformity coefficient decreased as a result of fatliquoring process. All the samples tested at tanning, retanning, dyeing and fatliquoring processes indicated no damage at 50,000 flexes. The study discussed these effects using transmission of fracture and damage mechanics in leather, structural implication of the resulting leather and existing models of materials.