Magnesium hydroxide is a new type of inorganic halogen-free flame retardant in recent years. It has multiple functions such as flame retardant, smoke suppression, drip prevention and filling. Compared with other flame retardants, it has a better smoke suppression effect. It is an eco-friendly flame retardant because it has no harmful substances discharged during production, use and disposal, and it can also neutralize the acidic and corrosive gases generated during combustion. The thermal decomposition temperature of magnesium hydroxide is 340 ° C, 100℃higher than aluminum hydroxide, it is conducive to speed up the extrusion speed, shorten the molding time, help to improve the flame retardant efficiency, and it can be widely used PE, PP, PVC, ABS, PS, HIPS, PA, PBT, unsaturated polyester, epoxy resin, rubber, paint flame retardant filler, chemical, environmental protection, etc.
1. Since the molecular negative polarity of magnesium hydroxide is very strong, the magnesium hydroxide powder is prone to agglomeration between particles. The result of this phenomenon directly causes that magnesium hydroxide will be difficult to disperse and be compatible in the polymer material, so simple magnesium hydroxide powder is generally not used as a flame retardant. Magnesium hydroxide used as a polymer material flame retardant must be provided with an ultrafine and surface coupling agent coating or modification treatment.
2. The magnesium hydroxide as flame retardant must be mixed well with the polymer raw materials in proportion. For example, when magnesium oxide is used as a flame retardant in PP, in order to make Mg(OH): uniformly dispersed in PP, a high-speed mixer, or a Buss Kerlader, or a twin-screw mixing extruder can be used. For example, all PP and toughening agent can be mixed with the required amount of 60% Mg(OH): firstly added to the mixing and kneading machine for a few minutes, and then the remaining Mg (OH) is added for the second time. If mixing with Mg(OH) in an internal mixer, in addition to using two addition methods, it is better to accurately measure the charging rate in the range of 87% to 93%. When the charging rate is small, the mixing effect is poor. When the charging rate is more than 95%, it is easy to cause the Mg(OH) agglomerating, and it is difficult to disperse evenly.
3. The general dosage of magnesium hydroxide as flame retardant is about 50%, but the user can adjust the dosage ratio according to the requirements of different materials and specific FR levels. It is recommended that when the added amount exceeds 80%, it can be suitably used in combination with other inorganic flame retardants to seek the best synergistic flame retardant effect. For example, 30% magnesium hydroxide and 30% aluminum hydroxide synergistically flame retardant is used in PE, which is much better than using a single flame retardant alone. (For example, it can be combined with antimony trioxide, zinc borate, red phosphorus, polyols, etc.).
4. Magnesium hydroxide flame retardant has strong smoke elimination ability. In the fire, smoke is the first and most lethal and delays the timing of firefighting. 80% of the deaths in the fires are caused by asphyxiation, so the contemporary "flame retardant" is compared with "smooth suppression". Moreover, "smoke suppression" is more important than "flame retardant" for certain high polymers such as PVC. Halogen- high-polymer and halogen-based flame retardants and antimony compounds are the main sources of smoke. Therefore, the halogen-free flame retardants is the main way to reduce the amount of smoke. The beauty of hydroxide is another important measure to solve the problem of smoking. Generally, the addition amount of 30% can achieve a good smoke suppression effect (for example, the density of smoke containing of 30% Mg(OH)2 in PP is only about 1/3 of that of inflammable PP).