Water-swellable rubber blend from epoxidized natural rubber and superabsorbent polymer composite

Abstract

Epoxidized natural rubber (ENR) and a superabsorbent polymer composite (SAPC) along with other minor components were mechanically blended in an internal mixer (Brabender Plasticorder) at 40°C and 60 r/min rotor speed with 80% fill factor. The SAPC was synthesized by grafting polyacrylamide onto hydroxyethyl cellulose backbones and adding bentonite clay. The first water-swelling behavior was investigated with alternative epoxidation levels of the ENR. Water-swellable rubber (WSR) performed well in terms of water absorbency, and weight loss was achieved with 50 mole% epoxidation level, so this ENR was chosen for the rubber matrix from which WSR was prepared with various contents of SAPC (0, 5, 10, 15, and 20 phr). The results indicated that SAPC loading positively affected water absorbency, which was resulted by increasing weight loss and loss of mechanical properties, such as tensile strength and elongation at break. However, the modulus increased with SAPC content. WSR formulated from ENR-50, SAPC, and other ingredients resulting in good water-swelling behaviors and modulus, while the tensile strength and elongation at break had opposition. SAPC was an important factor to control the overall WSR properties.