Hebei Messi Biology Co., Ltd. stated that magnesium hydroxide can lose crystal water at 340℃, and the product magnesium oxide after dehydration is a refractory material. Since the dehydration reaction is an endothermic reaction, the use of magnesium hydroxide can achieve low-smoke and halogen-free flame retardancy of polyolefin plastics. Magnesium hydroxide has three functions: filling, flame retardancy and smoke suppression. Compared with aluminum hydroxide, which has the same function, since its decomposition temperature is higher than the processing temperature of polyolefin plastics (180-220℃), the added magnesium hydroxide will not decompose in advance when filling plastic processing.
Magnesium hydroxide is a new type of filling flame retardant. It releases bound water when decomposed by heat and absorbs a large amount of latent heat to reduce the surface temperature of the synthetic material it fills in the flame. It has the function of inhibiting the decomposition of polymers and cooling the generated combustible gases. Magnesium hydroxide is an inorganic flame retardant filler for polymer-based composite materials with good application prospects. Like aluminum oxide, magnesium hydroxide flame retardant relies on chemical decomposition to absorb heat and release water when heated to play a flame retardant role. Therefore, it has the advantages of non-toxicity, low smoke, and the magnesium hydroxide generated after decomposition has stable chemical properties and does not produce secondary pollution.
However, compared with halogen-containing organic flame retardants, to achieve a comparable flame retardant effect, the filling amount generally needs to reach more than 50%. Since magnesium hydroxide is an inorganic substance, the compatibility between the surface and the polymer base material is poor. Such a high filling amount, if it is not surface modified, will lead to a decrease in the mechanical properties of the composite material after filling it into the polymer material. Therefore, it must be surface modified to improve its compatibility with the polymer base material, so that the mechanical properties of the filling material do not decrease, and even improve some of the mechanical properties of the material.
Unmodified magnesium hydroxide exists in the form of agglomerates in PP. Although the powder itself is extremely fine, there is a clear boundary or even a void between the particle agglomerates and the PP matrix due to the incompatibility of the particle surface with the PP matrix. The voids formed by the escape of magnesium hydroxide particles during brittle fracture indicate that the unmodified magnesium hydroxide only plays a role of filling and flame retardant in PP, and does not chemically bond with PP. The surface-modified magnesium hydroxide is evenly dispersed in the PP matrix, and most of the particles are dispersed in the material in the form of primary particles or small agglomerated particles.