Development history of Magnesium hydroxide flame retardant

Magnesium hydroxide is a new type of filled flame retardant. It releases bound water and absorbs a large amount of latent heat during thermal decomposition to reduce the surface temperature of the composite material it fills in the flame, which has the function of inhibiting polymer decomposition and cooling the generated combustible gas.

Magnesium hydroxide is a kind of inorganic flame-retardant filler for polymer matrix composites with good application prospects. Like Aluminium hydroxide, Magnesium hydroxide flame retardant plays the role of flame retardancy by absorbing heat and releasing water through chemical decomposition when heated. Therefore, it has the advantages of non-toxic, low smoke, stable chemical properties of magnesium oxide generated after decomposition, and no secondary pollution. However, compared to halogenated organic flame retardants, in order to achieve a considerable flame retardant effect, the filling amount generally needs to reach more than 50%. As Magnesium hydroxide is an inorganic substance, its surface has poor compatibility with the polymer base material. If such a high filling amount is not treated by surface modification, the mechanical properties of the composite will decline after being filled into the polymer material. Therefore, it is necessary to carry out surface modification treatment on it to improve its compatibility with polymer based materials, so that the mechanical properties of the filling material do not decrease, and even improve some of the mechanical properties of the material.

The experiment proves that the unmodified Magnesium hydroxide exists in PP as an aggregate. Although the powder itself is very fine, there is an obvious boundary or even a cavity between the particle aggregate and the PP matrix due to the incompatibility between the particle surface and the PP matrix. The cavity formed after the escape of Magnesium hydroxide particles during brittle fracture indicates that the unmodified Magnesium hydroxide only plays a filling and flame retardant role in PP, and does not form Chemical bond with PP. The surface modified Magnesium hydroxide is evenly dispersed in the PP matrix, and the particles are mostly dispersed in the material in the form of primary particles or small agglomerated particles.

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