Abstract: Magnesium hydroxide retardant,smoke and fill at the same time,has become a growing concern inorganic environment-friendly flame retardant materials. Research of online modified was made on magnesium hydroxide flame retardant by sodium dodecyl benzene sulfonate or polyvinyl alcohol.Then contrast settling propertise、filter performance、activation、oil absorption value and viscosity before and after modification. The stirring speed under the conditions of 200-300rpm,the experimental results show that:the best optimal amount of sodium dodecyl benzene sulfonate was 2.5%,the magnesium hydroxide magnitude sedimentation rate achieve 1.111×10-4m/s,increase 11 times nearly,cake specific resistance was reduced to 21.835×10-10m/Kg, activation grade reach to97.62%,oil absorption value decreased to 28.5mL/100gMg(OH)₂, viscosity reduced about 1/2 of unmodified;the best optimal amount of polyvinyl alcohol was 1.5%,the magnesium hydroxide magnitude sedimentation rate achieve 5.208×10-4m/s ,increase 50 times nearly,cake specific resistance was reduced to 20.779×10-10m/Kg,activation grade reach to97.73%,oil absorption value decreased to25mL/100gMg(OH)₂ and viscosity reduced about 1/2 of unmodified.

Key words: magnesium hydroxide, surface modification, sodium dodecyl benzene sulfonate, polyvinyl alcohol