Abstract

In this work a novel and eco-friendly retanning agent was developed to eliminate the potential risk of formaldehyde occurrence in leather along with improving the characteristics of leather. A series of sulfanilic acid modified melamine-glutaraldehyde resins were produced at varied mole ratios of melamine, glutaraldehyde and sulfanilic acid. The glutaraldehyde to melamine mole ratio (GL/M) was varied from 2 to 6 whereas the sulfanilic acid to melamine mole ratio (SNA/M) was varied from 0.5 to 3. The viscosity trend of resins in the series was studied.

Synthesised resins were used in retanning leather in comparison with a melamine-formaldehyde resin as a control. Retanned pieces of leather were evaluated for their mechanical properties and organoleptic properties. Samples of leather retanned with the optimal resin were also analysed for comparative free formaldehyde determination. Scanning electron microscopy was performed to study the morphology of grain surface and fibre structure of resulting leather. Effluent received from retanning process was analysed for pollution load estimation. The optimum resin was subjected to determination of its molecular weight, to thermo gravimetric analysis and FTIR. It was obvious from the results of this study that the optimal resin produced a leather with improved mechanical and organoleptic properties in comparison with the control.

Estimation of formaldehyde content in leather proved the complete elimination of free formaldehyde in leather whereas the level in control leather was 152mg/kg. Results from the pollution load study of waste water confirmed an improvement in efficiency of COD, TDS, TSS and formaldehyde by 13.40%, 9.71%, 8.82% and 100% respectively. SEM monographs of grain surface and collagen fibres showed better filling, distribution and reactivity of the optimal resin. Thermo gravimetric analysis proved the increase in thermal stability of developed resin by 16.3% as compared to control. The eco-friendly condensation polymer produced in this work was considered suitable for making formaldehyde-free leather with improved retanning properties, thermal stability and pollution load.