Preparation and properties of flame-retardant silicone rubber containing brucite powder and hydrotalcite
In the field of polymer materials, silicone rubber is widely used in aerospace, medical, electronic and electrical industries due to its excellent heat resistance, weather resistance and biocompatibility. However, the flammability of silicone rubber limits its use in places with high fire protection requirements. In order to improve the flame retardant properties of silicone rubber, researchers have explored the use of a variety of flame retardants, among which the compound use of hydrated magnesium silicate and hydrotalcite has shown good results.
Flame retardant mechanism of hydrated magnesium silicate and hydrotalcite
Both brucite and hydrotalcite are halogen-free flame retardants. They can absorb heat and release moisture during combustion, reduce the surface temperature of the material, and slow down the thermal degradation process. Brucite decomposes at high temperatures to form magnesium oxide and water vapor. Magnesium oxide can form a protective film on the surface of the material to prevent further transfer of oxygen and heat. Hydrotalcite also decomposes during combustion, releasing carbon dioxide and water vapor, while forming layered magnesium oxide and aluminum oxide, further enhancing the flame retardant effect.
Preparation method
Raw material preparation: Select brucite powder and hydrotalcite with high purity and moderate particle size as flame retardants.
Mixing and dispersion: Mix brucite powder and hydrotalcite in a certain proportion, and then disperse them evenly in the silicone rubber matrix by high-speed stirring or ball milling.
Vulcanization: The mixed flame retardant is vulcanized together with the silicone rubber matrix to form a composite material with flame retardant properties.
Performance evaluation
Flame retardant performance: The flame retardant grade of the material is evaluated by vertical burning test (such as UL-94 standard), and the oxygen index test (LOI) determines the minimum oxygen concentration for maintaining combustion.
Thermal stability: The thermal stability of the material is studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and the thermal degradation behavior of the composite material is analyzed.
Mechanical properties: The effect of the addition of flame retardant on the mechanical properties of silicone rubber is evaluated by tensile, tearing and hardness tests.
The study shows that the compound use of brucite powder and hydrotalcite can significantly improve the flame retardant properties of silicone rubber while maintaining good thermal stability and certain mechanical properties. Under the appropriate compounding ratio, the composite material can reach the V-0 flame retardant standard, and the oxygen index is significantly higher than that of pure silicone rubber. Thermogravimetric analysis shows that the thermal stability of the composite material is better than that of pure silicone rubber.
The combination of brucite powder and hydrotalcite as a flame retardant not only improves the flame retardant properties of silicone rubber, but also maintains its basic physical and mechanical properties, providing a new direction for the development of high-performance flame-retardant silicone rubber. This composite flame retardant strategy provides strong support for broadening the application field of silicone rubber, especially in industries with high fire safety requirements.