slow release rubber formulations containing ZnSO4

Styrene butadiene (SBR) and natural rubber (NR) can be used as binding matrices to control the release of zinc (Zn) which is a micro-nutrient for plants. The leaching rate of zinc in an aqueous medium depends on the concentration of zinc sulphate loaded in the two types of rubber used, the temperature of the surrounding environment and the pH of the aqueous medium. Water uptake was increased with increasing concentration of ZnSO₄. The sustained release of zinc ions from the investigated formulations was prolonged for over five months. The mechanical properties of the vulcanizates were affected as the concentration of zinc sulphate changed.