Rheological and thermodynamical behavior of styrene/butadiene rubber-organoclay nanocomposites

Organophilic layered silicate (montmorillonite type) was added up to 10 phr to a styrene/butadiene rubber (SBR) cured by an efficient vulcanization sy stem. The compounds were characterized in respect to their curing, rheologi cal and mechanical properties. In addition, attempt was made to consider so me thermodynamical aspects of the resulting network. The crosslink density, assessed by the Flory-Rehner equation, increased with increasing organocla y content. This was traced to the accelerator role of the amine functionali ty of the trialkyl-amine intercalant used. The pronounced structural viscos ity (i.e. viscosity decrease as a function of shear rate) and high elongati on at break of the compounds caused by the incorporation of organoclay were opposed to the enhanced crosslinking and reinforcing effect of the clay su pposed to the exfoliated. To solve the above contradiction a model was prop osed according to which the silicate layers are intercalated/exfoliated and encapsulated by a highly crosslinked rubber layer and these "rubberized" p latelets are embedded in the lightly crosslinked bulk.