Preparation of styrene butadiene copolymer–silica nanocomposites via differential microemulsion polymerization and NR/SBR–SiO2 membranes for pervaporation of water–ethanol mixtures

Abstract

• SBR–SiO 2 nanoparticles were prepared via differential microemulsion polymerization. • Modified-SiO 2 was completely encapsulated with SiO 2 as core and SBR as shell. • A high conversion and small particle size were obtained at a low SDS concentration . • NR/SBR–SiO 2 composites could be used as a novel membrane for pervaporation. • NR/SBR–SiO 2 membranes had high mechanical properties and water selectivity. Styrene butadiene copolymer (SBR)–SiO 2 nanoparticles with core–shell morphology were prepared via differential microemulsion polymerization. The effects of silica loading, monomer to water ratio, surfactant concentration and initiator concentration on monomer conversion, particle size, particle size distribution, grafting efficiency and silica encapsulation efficiency were investigated. A high monomer conversion of 86.6% and SBR–SiO 2 nanoparticles with a size range of 20–50 nm, with a narrow size distribution and high grafting efficiency of 75.5% were obtained at a low surfactant concentration of 3 wt.% based on monomer. The obtained SBR–SiO 2 nanoparticles exhibited spherical morphology with SiO 2 as the core and SBR as the shell as confirmed by TEM micrographs. Well-dispersed SBR–SiO 2 nanoparticles were successfully synthesized by differential microemulsion polymerization at a low surfactant concentration under optimum condition. A nanocomposite membrane prepared from natural rubber (NR) and a SBR–SiO 2 emulsion was tested for its mechanical properties and the pervaporation of water–ethanol mixtures. The flux and selectivity of NR/SBR–SiO 2 nanocomposite membranes were reported as a function of SBR–SiO 2 loading and water concentration. The NR/SBR–SiO 2 membranes can be used to separate water from mixtures of water/ethanol with high water selectivity.