Effect of magnetite nanoparticles and their surface modification on the mechanical and magnetic properties of silicon‐based magnetic elastomer nanocomposite

Silicon nanocomposites were prepared with unmodified and modified magnetite nanoparticles in order to study the effect of the fatty acid modification on the curing reaction and thereafter on the mechanical and magnetic properties of the filled silicon‐based elastomer. Magnetite nanoparticles were first surface modified with oleic and stearic acid. Silicon nanocomposites with unmodified and modified magnetite nanoparticles were prepared by predispersing the nanoparticles in the silicone with the curing agent using toluene and ultrasound assisted mixing. The effect of the magnetite on the crosslinking reaction was studied in a rubber process analyzer instrument. At first, the addition of 1 wt% of magnetite decreased the induction time and increased the maximum torque, but upon increasing the magnetite content, this time increased and the maximum torque decreased. However, all the nanocomposites showed an induction time much lower than that of the pure silicon and a maximum torque much higher than that of the pure silicon. Unmodified magnetite nanocomposites showed a heterogeneous saturation magnetization when magnetite nanoparticles were modified with oleic and stearic acid. This resulted in homogeneous and replicable properties, attributed to the improvement in nanoparticles dispersion and distribution within the polymer matrix. The high saturation magnetization values of composites with unmodified magnetite compared with those with modified magnetite confirm that modified magnetite presented the best dispersion and more homogeneous magnetic properties. The Fourier‐transform infrared spectroscopy analysis suggests that the magnetite nanoparticles coating could be reacting with the silicon hydrosilane group which in turn decreases the attainable crosslinking level. With respect to the tensile properties, the tensile stress, as well as the elongation at the breakpoint decrease, in general, with increasing the magnetite content. POLYM. COMPOS., 40:3981–3988, 2019. © 2019 Society of Plastics Engineers