Zinc Oxide in Natural Rubber Latex

Students: We are a group of students studying the effect of ZnO in ammoniated natural rubber latex concentrate. We hope you could help us with some information on the solubility of ZnO in natural rubber latex especially the effect of pH.
 
John Woon (Senior Latex Consultant): I am assuming you are already familiar with the phenomenon of "ZnO thickening due to Zinc-amine complex".

Studies had been done on the factors controlling the solubility of ZnO in Hevea natural rubber latex using model solutions containing ammonia and ammonium salt at a given pH. It had been found that the solubility of ZnO in the latex is proportional to the total concentration of ammonia and ammonium salt.

Also, at a constant concentration of free ammonia and ammonium ions, maximum solubility of ZnO can be achieved at a pH of 9.5.