Magnesium oxide synthesized with Alpinia zerumbet leaf extracts as a sustainable alternative to zinc oxide in nitrile rubber compounds: A comparative vulcanization kinetics investigation

Abstract

AbstractZinc oxide (ZnO) is the most widely used activator in the rubber industry; however, there is growing concern about its use as it can become toxic to the environment, particularly in aquatic systems. This study describes the synthesis of magnesium oxide (MgO) assisted by the Alpinia zerumbet extract, which is then used as an activator in the replacement of ZnO to vulcanize nitrile rubber (NBR) containing 33% and 45% acrylonitrile (ACN). The t90 for NBR‐33% and NBR‐45% are 20 and 15 min, respectively. This indicates a reduction of 5 min in t90 with an increase in ACN. In comparison, ZnO‐activated NBR compounds exhibit the opposite trend, with t90 increasing from 10 for NBR‐33% to 19 min for NBR‐45%. Furthermore, the decrease in activation energy (Ea) with the increase in conversion for 33%‐MgO and 45%‐MgO indicates that vulcanization with MgO is a complex process. This behavior is comparable to that of 45%‐ZnO, but not for 33%‐ZnO because its Ea remains oscillating at 80–90 kJ mol−1 in the entire conversion range. The crosslink densities of 33%‐MgO and 45%‐MgO are 5.87 and 4.78 mol cm−3, respectively. These values are slightly higher than those for 33%‐ZnO (5.77 mol cm−3) and 45%‐ZnO (4.38 mol cm−3).