JOURNAL OF COMPOSITE MATERIALS Article Investigation of thermal and mechanical properties of styrene–butadiene rubber nanocomposites filled with SiO 2 – polystyrene core–shell nanoparticles Mujahid Khan 1 , Satyendra Mishra 2 , Debdatta Ratna 3 , Shriram Sonawane 4 and Navinchandra Gopal Shimpi 1 Abstract The present study investigates the effect of SiO 2 –polystyrene core–shell nanoparticles on properties of styrene–buta- diene rubber nanocomposites. Meanwhile, SiO 2 –polystyrene core–shell nanoparticles were synthesized under con- trolled ultrasound assisted microemulsion technique. Further, as-synthesized SiO 2 –polystyrene nanoparticles were subjected to various characterization techniques, such as X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, and Fourier transform infrared spectroscopy to know its size, shape, and presence of functional groups. The average diameter of SiO 2 –polystyrene nanoparticles was found to be 45 nm. SiO 2 –polystyrene nanoparticles were reinforced in styrene–butadiene rubber using two-roll mill and molded on compression molding machine, which then subjected to various testings (X-ray diffraction, field emission scanning electron microscope, thermogravimetric analysis, and universal testing machine). Moreover, the crosslinking density was investigated using solvent sorption technique. The properties of styrene–butadiene rubber nanocomposites were found to be improved with increasing amount of SiO 2 –polystyrene nanoparticles (2.0 wt%) and decreases subsequently (2.5 wt%). This enhancement in properties was due to uniform dispersion of core–shell nanoparticles with embedded chains of rubber. Also this enhancement in properties was due to smooth surface of core–shell nanoparticles (2.0 wt%) and decreases subsequently at higher amount of loading (2.5wt%). However, the minimal crosslinkage leads to more solvent sorption, which leads to increase in average molecular weight. This decrement in the crosslinkage density with increase in average molecular weight was due to voids or free volume inside the matrix, which allows the solvent to get penetrated inside the matrix. This effect was not due to styrene–butadiene rubber matrix but due to shell of polystyrene over SiO 2 . Keywords Styrene–butadiene rubber, SiO 2 –polystyrene nanoparticles, mechanical properties, thermal properties, morphology Introduction Nowadays, nanoscience and technology gaining the fast momentum in the field of polymer science and tech- nology due to drastic improvement in properties of materials as compared to bulk. 1–4 Due to addition of nano size materials such as SiO 2 , 5 TiO 2 , 6 CaCO 3 , 7 CaSO 4 , 8 Mg(OH) 2 , 9 MMT, 10,11 Cu, 12 CNTs, 13 and ZnO, 14 properties of polymer nanocomposites (optical, electrical, mechanical, thermal, and physical properties) were found to be improved drastically even at lower amount of loading. 15–17 This enhancement is due to 1 Laboratory for Material Sciences, Department of Chemistry, University of Mumbai, India 2 University Institute of Chemical Technology, North Maharashtra University, India 3 Naval Materials Research Laboratory, DRDO, India 4 Department of Chemical Engineering, Visvesvaraya Institute of Chemical Technology, India Corresponding author: Navinchandra Gopal Shimpi, Laboratory for Material Sciences Department of Chemistry, University of Mumbai, Santa Cruz(E) 400 098, India. Email: navin_shimpi@rediffmail.com Journal of Composite Materials 0(0) 1–11 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0021998319886618 journals.sagepub.com/home/jcm