Preparation of water swellable rubber from epoxidized natural rubber and sodium acrylate by in‐situ polymerization: Effect of vulcanization system, epoxide, and dicumyl peroxide, and sodium acrylate content

Abstract Water swellable rubber (WSR) was prepared from epoxidized natural rubber (ENR) and sodium acrylate (NaAA) by in‐situ polymerization using sulfur and dicumyl peroxide (DCP) as a vulcanizing agent and an initiator, respectively. The ENR, NaAA, and other additives were mixed in an internal mixer and a two‐roll mill. The effect of the vulcanization system, epoxide, and DCP, and NaAA content on the vulcanization, physical, and mechanical properties of WSR were investigated in this research. As the results, the scorch and curing time of WSR compounded with ENR 25 and vulcanized with a mixture of sulfur‐peroxided or mixed vulcanization system were less than other systems. Furthermore, the scorch and curing time decreased with the increase in DCP content. The WSR with ENR 50 vulcanized with DCP (1.5 phr) in the mixing system provided the highest tensile strength. However, the volume change of WSR with the mixing system (WSR/M) was lower than the WSR cured with peroxide (WSR/P). For WSR/P, the tensile strength, hardness, and volume change in water increased with increasing DCP, and NaAA content, while the elongation at break decreased. These results suggest that WSR has the potential for diverse applications, including waterproofing and sealing solutions in civil construction projects. Highlights Water swellable rubber (WSR) was prepared from epoxidized natural rubber (ENR) and sodium acrylate (NaAA) by in‐situ polymerization using sulfur and dicumyl peroxide (DCP) as a vulcanizing agent and an initiator. The scorch and curing time of WSR compounded with ENR 25 and vulcanized with a mixed vulcanization system were less than those of other systems. During the vulcanization process, ENR 50 can be generated by the ring‐opening of the adjacent epoxide groups more than ENR 25, and the self‐crosslink of ENR 50 was higher than ENR 25. Water swelling and volume change of WSR tended to decrease with increasing epoxide, and DCP content, whereas those properties increased with increasing NaAA content. Tensile strength, elongation at break, and hardness of WSR with the mixing system (WSR/M) were higher than those of WSR with the peroxide system (WSR/P). Swelling and volume change of WSR/P were higher than those of WSR/M.