Brabender-mixed blends of poly( acrylic acid) (PAA) and epoxidized natural rubber (ENR) were extruded through the capillary in a Monsanto processability tester, and the capillary pressure versus extrusion time plots were recorded. Constancy in capillary pressure with extrusion time was observed in the case of PAA/ENR blend; but the same blend, filled with HAE carbon black filler, shows a steady increase in capillary pressure with extrusion time. In presence of a free radical acceptor like thiophenol, the rate of capillary pressure rise decreases. Measurements of physical properties, swelling studies, and scanning electron microscopy photomicrography of the extrudates indicates the occurrence of a chemical interaction between physisorbed ENR and chemisorbed PAA.