Study On The Preparation Of Flame-retardant Nano-magnesium Hydroxide Modified By Polyacrylate Microemulsion

Magnesium hydroxide,an inorganic flame retardant,has become a hot topic in the field of flame retardants due to its advantages of good thermal stability,non-toxicity,smoke suppression and low price.However,common magnesium hydroxide used as flame retardant still has some shortcomings,such as large amount of filling required,hydrophilic and oil-phobic surface,poor compatibility with polymer matrix,resulting in weak properties of the filled material and so on.In order to solve these problems,on the one hand,it is necessary to reduce the particle size of magnesium hydroxide and increase the specific surface area of magnesium hydroxide to reduce the filling amount of flame retardant;On the other hand,the surface modification of magnesium hydroxide is carried out to change its surface properties from hydrophilic to lipophilic,thereby increasing its dispersibility in polymer materials.Nowadays,ultrafine particle size and surface modification of common magnesium hydroxide have become the focus of scientific research.However,there are few reports on the preparation of modified nano-sized magnesium hydroxide by using microemulsion as dispersant and modifier.In this paper,the new polyacrylate microemulsion as dispersant and modifier,and using three different process methods to prepare modified nano-magnesium hydroxide flame retardant,including the following parts:(1)Modified nano-sized magnesium hydroxide was prepared from magnesium chloride hexahydrate and sodium hydroxide with a new polyacrylate emulsion as dispersant and modifier in situ by mechanical mixing.The optimal reaction conditions of this preparation process were explored as follows:under normal temperature and pressure,m(polyacrylate)/m(Mg(OH)₂)=0.8,reaction at a stirring rate of 4000 rpm for 4 h;The comparison of characterization tests shows that the modified nano-sized magnesium hydroxide prepared under these conditions has perfect crystal form,regular nano-sheet shape,uniform particle size distribution and no agglomeration phenomenon.The measured contact Angle is about 102°,which showed good hydrophobic and lipophilic properties.(2)Modified nano-sized magnesium hydroxide was prepared by mechanical mixing with nano-sized magnesium hydroxide slurry as raw material and new polyacrylate emulsion as modifier.The optimum reaction conditions of this modification were found as follows:under normal temperature and pressure,m(polyacrylate)/m(Mg(OH)₂)=0.6,reaction at a stirring rate of 4000 rpm for 4 h;Compared with the samples modified by other modifiers,it was found that the nano-magnesium hydroxide modified by new polyacrylate emulsion had better dispersion,and the contact Angle of 109°was much higher than that of the samples modified by other modifiers.The results show that the new polyacrylate as modifier has better modification effect.(3)Modified nano-sized magnesium hydroxide was prepared by ball milling with common commercially available magnesium hydroxide as raw material and new polyacrylate emulsion as dispersant and modifier.The optimal reaction conditions for this preparation process were explored as follows:under normal temperature and pressure,m(polyacrylate)/m(Mg(OH)₂)=0.6,and react for 3 h at the working speed of the ball mill at 300 r/min;Characterization and test of modified nano-sized magnesium hydroxide prepared under these conditions,the results show that this process can complete the surface modification of common commercially available magnesium hydroxide while nanocrystallization,and achieve a good effect.