Abstract

The influence of solvents on combination tanned leather was established with observation of thermal stability, and the microstructure of the leather sample before and after shrinkage. Thermal stability of leather tanned with MI (mimosa), GA (glutaraldehyde), OZ (oxazolidine) and Al (aluminum sulphate) were reported using the shrinkage temperature for helix and random coil transition after soaking in 0.5, 1.0 and 2.0 mol/L urea solution, (pH4.0, 6.0 and 10.0) water, colza oil, glycerin and engine oil. The shrinkage temperature(Ts) of all leather samples was decreased by soaking in these solvents. The concentration of urea solution had a very obvious effect on GA-MI and MI-OZ-tanned leather, whose Ts reduced to 84.2°C and 84.6°C from 94.8°C and 100.9°C respectively. The influence of acidity and basicity of the solution also cannot be ignored, and OZ-MI leather was the most susceptible one whose Ts reduced to 85.3°C from 97.7°C The thermal stability of leather involving MI and Al can be affected remarkably by glycerin. All of the leather samples showed a more obvious Ts decrease when it was soaked from the dry state than in moist state.

Scanning electron microscope (SEM) studies revealed that the microstructure of collagen is destroyed when it shrinks and that the degree of destruction depends on the cross-linking agents.