Study On Preparation And Application Of Hexagonal Magnesium Hydroxide Flame Retardant

With the excellent properties of thermal stability, non-toxic, low cost and nopoisonous or harmful gas release during burning, Mg(OH)2becomes a kind ofenvironmentally friendly flame retardant which can be used in polymer materials,such as plastic, rubber, coating, to prevent them from burning. The purpose of thiswork is to prepare the hexagonal magnesium hydroxide flame retardant with smallparticle size, low surface polarity and high dispersion. Two parts are included in thiswork and are described below:First, in order to reduce the agglomeration of Mg(OH)2and to improve thecompatibility with polymers, hexagonal magnesium hydroxide with a mean particlesize of1μm was prepared. The influence of different hydrothermal conditions on thegrowth of crystal, especially on (001) plane, was investigated. The experimentalresults indicate that lower initial particle size and solid content of raw material,improve sodium hydroxide concentration and temperature, extend time are allconducive to the crystal growth. The growth direction of crystal is changed andshielding effect on (001) plane increases when the sodium hydroxide concentration isgreater than8mol/L or the time exceeds10h. The phenomenon is explained by thepolyhedron growth unit theory mode. Enlargement experiment of magnesiumhydroxide preparation is investigated in two kinds of high solid content of rawmaterial.Secondly, the application of magnesium hydroxide flame retardant is studied.The effects of three kinds of magnesium hydroxide on mechanical properties, flameretardant performance, rheological properties and crystallization behavior of PE areinvestigated. The results show that the flame retardant performance of PE is improvedby magnesium hydroxide, and OI is increased from19.2%to22.6%. The tensilestrength of PE can be effectively improved when adding hexagonal magnesiumhydroxide, but the elongation at break decreased from231.65%to28.78%, while themechanical property of PE is less affected by modified magnesium hydroxide. Thecrystallization rate of PE is accelerated because of heterogeneous nucleation effect,and the crystallinity decreases with the increase of content of magnesium hydroxide.In addition, the pseudoplastic of PE is enhanced and rheological properties areweakened when adding magnesium hydroxide or modifier.