Synthesis and characterization of three kinds of nano SiO₂ particles with different morphologies and their application in reinforced polyurethane grouting composites

Three kinds of SiO₂ sols containing amorphous nano-silica (nano A-SiO₂), spherical nano-silica (nano S-SiO₂), and layered hexagonal nano-silica (nano LH-SiO₂) particles were controllably synthesized by tailoring the hydrolysis of sodium silicate. By in-situ reaction between SiO₂ sols and hydrophilic polyurethane (HPU) prepolymer, synthesizing from diisocyanate and polyether polyol, a series of nano-silica modified hydrophilic polyurethane composites (nano SiO₂/HPU) were obtained. The structure and properties of HPU and nano SiO₂/HPU were characterized by ATR-FTIR, TEM, SEM and mechanical properties. The results show that PEG plays a regulating role in the formation of nano-silica particles in SiO₂ sol, and the morphology of nano-silica particles affects the mechanical properties of nano SiO₂/HPU grouting composites differently. Specifically, nano S-SiO₂/HPU exhibits higher compression strength, and nano LH-SiO₂/HPU possesses better toughness.