Walnut shell ash as a sustainable material for compounding with bromobutyl rubber for tire inner liner applications

This paper reports walnut shell ash (WNS ash) a sustainable material for tubeless inner liner application. This sustainable material replaced the commercial magnesium oxide (MgO).The WNS ash generated at 550 degrees C, is found to have 72% alkali metal and alkali earth metal, whereas commercial MgO shows 95% alkali metal and alkali earth metal. It was observed in this study WNS ash perform as cure retarder in bromobutyl rubber/bromo isobutylene isoprene rubber-based tube less inner liner compound and its performance was similar with commercial MgO; however, not exactly equivalent. Optimum cure retardation found at 0.40 phr loading with WNS ash. Interestingly, due to sulfur (S) and zinc (Zn), the WNS ash produced some cure activation effect. Cure rate was observed for 0.40 phr WNS ash load in gum/filled formulations at 35/15 minutes(-1)compared to 30/10 minutes(-1)in commercial MgO at 0.30 phr. Physical properties of compound made with 0.40 phr WNS ash and 0.30 phr MgO found comparable in both gum and filled system. Alkali metal and alkali earth metal of WNS ash at 0.40 phr loading is equivalent to 0.30 phr of MgO. This material is an important gateway in the rubber industry as a multifunction sustainable material.