Carboxylated nitrile rubber and ISAF carbon black chemically interacted when the mix of the two was extruded at high temperature (180 degrees C) in a Monsanto Processibility Tester. Studies on the physical properties of the extrudates and the reaction kinetics of the extrusion process showed that the extent of interaction increased with increase in filler loading, oxygen-containing functional groups on the filler surface, shear rate, extrusion time, and the loading of (3-aminopropyl) triethoxysilane.