Plastic is a commonly used material in industrial production and daily life. Plastics are easy to burn and produce a large amount of toxic and harmful substances and smoke when burning. Effectively improving the flame retardancy of plastics is a problem that needs to be solved in practical applications. Magnesium hydroxide (MH) is an environmentally friendly green inorganic flame retardant. It has good flame retardant, smoke suppression and filling effects. It has a high decomposition temperature and does not produce toxic and harmful pollutants when it decomposes. At the same time, Magnesium hydroxide can be combined with other Flame retardants are used synergistically to achieve higher flame retardant effects.
Application of magnesium hydroxide flame retardant in PP
PP has low toxicity, low cost, good electrical insulation, good processability and chemical corrosion resistance, and meets the application requirements in automobiles, construction and other fields. However, PP is easy to burn and burns quickly. It produces molten droplets during the combustion process and releases a large amount of toxic smoke. Therefore, it is important to improve the thermal resistance of PP. Chen Lingzhi et al. used magnesium sulfate, ammonia and activated carbon as raw materials to prepare activated carbon modified Magnesium hydroxide flame retardant and applied it to PP polymer. The results show that when the modified Magnesium hydroxide flame retardant is applied to PP, the limiting oxygen index (LOI) of PP is increased from 19.6% to 28.9%, significantly improving its flame retardant performance.
Application of magnesium hydroxide flame retardant in polystyrene (PS)
PS has the characteristics of low price, easy processing, corrosion resistance, strong impact resistance, and good durability. It is widely used in construction, decoration, electrical, transportation and other industries. PS has a low LOI value, is easy to burn, and can continue to burn after leaving the fire source. During the combustion process, it releases a large amount of heat, toxic smoke, and produces severe droplets, which limits its wide application. Researchers added Magnesium hydroxide to PS to study the changes in its flame retardant effect. The results show that with the increase in the amount of Magnesium hydroxide added, the CO2 generated during the thermal degradation of PS continues to decrease, the amount of residual carbon increases sharply, and the content of volatiles and semivolatiles increases, indicating that the addition of Magnesium hydroxide changes the flame retardancy of PS and improves it. It increases its combustion temperature and changes its combustion mechanism.
Application of magnesium hydroxide flame retardant in PVC
PVC is also a common thermoplastic general-purpose plastic. It is widely used in fields such as films, pipes, wall panels and electrical materials (especially cable insulation sheaths). It can be divided into hard PVC and soft PVC. Rigid PVC adds less plasticizer, and its flame retardant properties are better than soft PVC. However, PVC contains chlorine, which produces hydrogen chloride gas when burned and decomposed, as well as a large amount of toxic and harmful smoke. Therefore, while improving the flame retardancy of PVC, you also need to pay attention to the large amount of smoke generated when PVC is burned.
Magnesium hydroxide flame retardant can improve the flame retardant performance of PVC while reducing the emission of toxic and harmful gases, and can be used in PVC composite materials. Wu Jianning et al. used different modifiers to surface modify Magnesium hydroxide, and studied the impact of modified MH on the mechanical properties and flame retardant ability of PVC. The results show that using zinc stearate as the modifier has the best modification effect, with an oil absorption value of 33.39%. The obtained Magnesium hydroxide particles are dispersed evenly, the agglomeration phenomenon is significantly improved, and the flame retardant ability of PVC is significantly improved. However, for The tensile strength of PVC plays a role.
Application of magnesium hydroxide flame retardant in PE
PE has excellent processability, electrical insulation, mechanical properties and high and low temperature resistance. It is widely used in construction, electrical, medical and other industries. However, its LOI value is only about 17.4% and it is easy to burn, which limits its application scope. Improving the flame retardancy of PE is also a hot topic of research. Commonly used flame retardants for PE include halogen, phosphorus and nitrogen, aluminum/magnesium inorganic flame retardants, etc., but Magnesium hydroxide is favored because of its low cost and environmental friendliness.
Messi Biology used magnesium hydroxide with three different particle sizes as a flame retardant, mixed it with PE to make composite materials, and studied its mechanical properties, electrical properties, thermal stability and flame retardant properties. The results show that Magnesium hydroxide can significantly improve the flame retardancy and thermal stability of PE. When the Magnesium hydroxide particle size is 3.1 μm, the composite material has the best overall performance, with a tensile strength of 16.1 MPa, elongation at break of 400%, and LOI The value is 22.3%, the peak heat release rate (PHRR) is 270 kW/m2, and the volume resistivity is 5.2×1013Ω·m.
Challenges and prospects of magnesium hydroxide flame retardants
Although magnesium hydroxide is a green, environmentally friendly, flame retardant material with excellent flame retardant effect and low cost, it can be widely used in the plastics industry. However, since Magnesium hydroxide is an additive flame retardant, it needs to be added in large amounts to achieve high retardancy. flammability requirements; and Magnesium hydroxide has strong polarity and strong hydrophilicity, is not easy to disperse in polymers, and is prone to agglomeration, which will lead to poor compatibility with plastics, a decrease in the strength of the composite plastics produced, and processing The stability and fluidity become poor, limiting its large-scale application in the plastics industry.
In the future, we can improve the flame retardancy of Magnesium hydroxide and improve its compatibility with plastics by strengthening the ultra-fine refinement of Magnesium hydroxide, developing new surface modifiers, compounding with other flame retardants, and conducting research on microencapsulation technology. Reduce its impact on the mechanical properties of plastics, thereby expanding the application of Magnesium hydroxide in the field of plastic flame retardancy.