Study on the preparation and characterization of high-dispersibility nanosilica

This article reports on experiments aimed at modifying nanosilica powder by adding a silane coupling agent, KH570, to achieve high dispersibility and strengthen the compatibility and interface bonding between it and the organic phases. Experiments were first done to prepare the common nanosilica powder, dried at 120°C for 4 h in a drying oven; second, an ethanol/water solution (volume ratio 11:1, total volume not more than two-thirds of the capacity of the flask) was blended in a three-necked flask with a reflux condenser and magnetic stirring; third, appropriate amount of dried nanosilica powder and appropriate mass fraction ratio of the silane coupling agent KH570 were added into the ethanol/water solution, and the pH of the mixture was adjusted to about 4–5 by adding acetic acid solution; fourth, the three-necked flask was placed in a water bath, and the modification reaction of the above mixing solution was sustained for an appropriate time in the appropriate temperature with magnetic stirring; fifth, the above mixing solution was separated by using a centrifuge (10,000 rpm) for 3 min, and the precipitate at the bottom of the flask was obtained after the supernatant was poured out; sixth, the precipitate was dried at 120°C for 48 h in a drying oven after it was washed with acetone several times, finally yielding the high-dispersibility nanosilica powder. The orthogonal test method was adopted to optimize three key test parameters: mass fraction ratio of the silane coupling agent KH570, modification reaction temperature, and modification reaction time. The dispersion effect of the high-dispersibility nanosilica powder was characterized by using infrared, X-ray diffraction, and scanning electron microscopic analyses from different views. The results revealed that the best dispersibility effect was achieved when the mass fraction ratio of the silane coupling agent KH570 was 3%, the modification reaction temperature was 80°C, and the modification reaction time was 2 h. Furthermore, the modification reaction resulted in chemical bonding, but not simple physical adsorption, owing to the presence of organic bond groups in the nanosilica modified by the silane coupling agent. The crystal structure of the nanosilica powder remained amorphous after the modification reaction.