May 29, 2023
The principle and advantages of magnesium hydroxide flame retardant
Magnesium hydroxide is an inorganic flame retardant filler, which has a broad application prospect in polymer-based composite materials. Magnesium hydroxide flame retardant decomposes and releases water when heated, absorbs heat, reduces the temperature of the flame on the surface of the polymer material, and delays the process of polymer degradation into low molecular weight. At the same time, the released water vapor can dilute the oxygen on the surface of the material, inhibiting the combustion of the material surface. Therefore, magnesium hydroxide flame retardant has the advantages of non-toxicity, low smoke, and no secondary pollution. It is an environmentally friendly flame retardant.
The necessity of modifying magnesium hydroxide
However, compared with halogen-based flame retardants, magnesium hydroxide flame retardants require a higher filling amount to achieve the same flame retardant effect, generally above 50%. Because magnesium hydroxide is an inorganic substance, it has poor compatibility with polymer-based materials. A high filling amount will affect the mechanical properties of composite materials. To solve this problem, it is necessary to modify the surface of magnesium hydroxide to improve its compatibility with polymer-based materials, improve its dispersibility in composite materials, increase its surface activity, thereby reducing its dosage, improving its flame retardant efficiency, and maintaining or improving the mechanical properties of composite materials.
The methods of modifying magnesium hydroxide
At present, there are two common methods for modifying magnesium hydroxide: dry method and wet method. The dry method modification is to mix dry magnesium hydroxide with an appropriate amount of inert solvent, spray it with a coupling agent or other surface treatment agent, and mix it in a low-speed kneading machine for modification treatment. The wet method modification is to suspend magnesium hydroxide in water or other solvents, directly add a surface treatment agent or dispersant, and modify it under stirring. The two methods have their own advantages and disadvantages and need to be selected according to specific situations. In addition to the surface modification method, the refinement method can also be used to crush magnesium hydroxide powder to the nanometer level, increase its contact area with the polymer matrix, enhance its affinity with the polymer, and thereby improve its flame retardant effect.