Effect of particle size and content of SiO₂ solvent-free nanofluid on mechanical and thermal properties of epoxy resin

To improve the dispersibility of the silicon dioxide (SiO2) and investigate the effect of particle size on the properties of matrix, 50, 90 nm and 220 nm nano-SiO2 were prepared by Stöber method, and SiO2 nanofluid (NF) was prepared by grafting the organosilanes and polyether amine on the surface of SiO2nanoparticles. Chemical structure and physical morphology of nanofluid were investigated by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties of SiO2 nanofluid/epoxy resin (NF/EP) composites with different particle sizes and different contents were studied, the results indicate that the mechanical properties of composites are increased first and then decreased with the increase of content. The 50 nm SiO2nanofluid has the best effect on improving impact strength, the impact and bending strength of epoxy resin are enhanced by 54.55% and 11.64% with the 1 phr addition. The 220 nm SiO2nanofluid has the best effect on improving bending properties, the impact and bending strength of epoxy resin are enhanced by 50.00% and 17.51% with the 1 phr addition. The results of the DSC and linear expansion coefficient tests show that the NF/EP composites have higher glass transition temperature and lower linear expansion coefficient than pure epoxy. Thus, with adequate mechanical properties and low coefficient of thermal expansion, NF/EP composites can be considered as promising candidates in the electronic packaging fields