Plasticizing Polystyrene with Waste Leather Buffing Dust: A Drive towards Waste-Polymer Composite Synthesis

This is the first report on the use of waste chrome-tanned Indian leather buffing dust for plasticizing atactic polystyrene (PS). There is no effective re-use of waste leather buffing dust reported till today. This waste material, after preliminary characterization, has been dispersed in solvated polystyrene. Resultant composites prepared therefrom via solution cast method exhibit a drastic drop in surface hardness up to certain modifier concentration, beyond which it increases. Addition of surfactants during dispersion of the buffing dust at the optimum level further reduces surface hardness. Para-toluene sulphonic acid (PTSA) has been found to be a better compatibilizer than more conventional sodium lauryl sulphate (LS) in this system. The compatibilized composites show substantial “yield behaviour” when stretched and the breaking strain has been improved drastically from 0.2% in pure polystyrene to 25% in PTSA compatibilized system without any loss in strength. Accordingly, the breaking energy has been increased to much greater than that of the virgin polymer. Effective plasticization of the composites has lowered the glass transition temperature (Tg); PTSA containing composite has shown the minimum value, possibly due to generation of more free volume around the rigid polystyrene molecules on account of its effective adsorption over finer dust particles. Accelerated thermal degradation study shows greater thermal stability of the composites as compared to virgin polymer and this possibly resulted due to the presence of chromium content in the waste, which acts as heat sinks.