Principle of inorganic flame retardant

The flame retardant mechanism of metal hydrate is that crystal water is released when it is decomposed by heat. This is a strong endothermic reaction that absorbs a lot of heat and can cool the polymer. At the same time, the water vapor produced by the reaction can dilute the combustible gas and inhibit the spread of combustion. Moreover, the new refractory metal oxides (Al2O3, MgO) have high activity, which will catalyze the thermal-oxidative crosslinking reaction of polymers and form a carbonized film on the surface of polymers. Carbonized film will weaken the heat and mass transfer effect during combustion, thus playing a role in flame retardant. In addition, such oxides can also adsorb smoke particles and play a role in suppressing smoke. The hydroxide flame retardant also has the functions of droplet resistance, carbonization promotion, non-volatilization, non-exudation and long-term retention in polymers. But the flame retardant effect of hydroxide is closely related to its dosage. The flame retardancy of the polymer increases rapidly with the increase of dosage, and the oxygen index is above 26, so it is a flame retardant material. However, high dosage will definitely affect the processability and mechanical properties of the substrate, and the compatibility of the material will be greatly reduced.

Ultrafine particle size, surface modification and synergistic composite technology are three main development directions. The surface of nano-sized magnesium hydroxide was modified by grafting low-density polyethylene for PA66 flame retardant, and compared with the traditional silane coupling agent KH550 modified magnesium hydroxide. The results show that the magnesium hydroxide grafted with LDPE has good dispersibility and excellent flame retardant effect. When the dosage is 40%, the oxygen index of PA66 can reach 365,438+0, and the flame retardant grade is V-0.