Nano-SiO2

with large specific surface area and numerous uncoupled surface atoms

has ability of combine physically and chemically with resin matrix strongly to strengthen and toughen resin.Nano-SiO2 was uniformly dispersed in water soluble phenol-formaldehyde resin by simple co-blended process and by ultrasonic dispersing solution co-blended process

respectively.Effects of nano-SiO2 on mechanical properties of resin coated sand were investigated by testing compressive strength of modified resin coated sand

and the optimized nano-SiO2 content for modification of resin was presented.Dispersed difference of nano-SiO2 particles in resin matrix by simple co-blended process and in solution co-blended process was analyzed by SEM.Results show that ultrasonic dispersing solution co-blended process is superior to simple co-blended process in dispersing nano-SiO2 particles into phenol-formaldehyde resin to greatly improve the mechanical properties of the resin.However

with excessive nano-SiO2

mechanical properties of the resin are deteriorated as a result of occurrence of easy aggregation.The optimized fraction of nano-SiO2 is 3% of the resin mass by experimental testing.