Excellent mechanical performance and enhanced dielectric properties of OBC/SiO₂ elastomeric nanocomposites: effect of dispersion of the SiO₂ nanoparticles

Two kinds of fumed SiO₂ nanoparticles with the same average diameter but distinct surface characteristics (hydrophilic A200 and hydrophobic R974) were incorporated into an ethylene-α-olefin block copolymer (OBC) to prepare high-performance thermoplastic elastomeric nanocomposites via simple melt mixing. Hydrophilic A200 exhibits a particular chain-like distribution while hydrophobic R974 shows a homogenous dispersion in the nanocomposites. The rheological percolation threshold of OBC/A200 nanocomposites was much lower than that of OBC/R974 nanocomposites, showing a more developed nanoparticle network in OBC/A200 nanocomposites. Thermodynamic analysis revealed that the particular chain-like distribution of A200 and more developed network structure are due to the selective localization of hydrophilic A200 in the melt. The reinforcement effect of hydrophilic A200 in OBC/A200 nanocomposites is always higher than that of hydrophobic R974 in OBC/R974 nanocomposites at the same filler loading, and even better, the increments in the tensile modulus of OBC/A200 nanocomposites are almost four times higher than that of OBC/R974 nanocomposites at the same silica loading. Besides, the dielectric permittivity of the OBC/A200 composite at low frequency was also higher than that of the OBC/R974 composite with the same loading of filler at the same frequency. These results provide guidance for the preparation of high-performance elastomeric nanocomposites with both excellent mechanical performance and enhanced dielectric properties.