Effect of the surface chemistry of kaolin on the properties of filled rubber compounds

Abstract

An attempt has made to activate the inert structure of Rubber grade kaolin clays through ion-exchange process. Counter ions absorbed by unsatisfied silicon, oxygen and hydroxyl ions at the edges of planar surfaces of kaolinite mineral to preserve electrical neutrality were replaced with complex organic ions containing active functional groups (amine, hydroxyl, carboxyl) in their organic radicals. Strongly attached to the clay surface these complex ions project their organic aryl or alkyl radicals outwards to suspending medium rubber matrix making inorganic kaolin surface effectively organic and therefore hydrophobic one. Such change in kaolin surface facilitated rubber- filler interaction owing to better wetting of the filler surface with organic rubber polymer and formation of sufficient density grafted polymer layer bonding the rubber matrix to filler. Carried out physico-mechanical testing of filled rubber compounds showed that modification of kaolin with chosen basic electrolytes ionized in aqueous medium was effective. Increase in strength characteristics has made possible in commercial practicability of rubber formulation technology the substitution of expensive reinforcing fillers with lowest in cost appropriately modified kaolin Clay.