Study on the composite of silicone rubber reinforced magnesium hydroxide and red phosphorus flame retardant high impact polystyrene

High-impact polystyrene (HIPS) is widely used in home appliances, automobiles and packaging industries due to its excellent mechanical properties and processing convenience. However, the flammability of HIPS limits its application in fields with high flame retardancy requirements. To this end, researchers aim to improve the flame retardant properties of HIPS by adding flame retardants such as magnesium hydroxide and red phosphorus and utilizing the synergistic effect of silicone rubber (SR). This study explores the flame retardant mechanism of this synergistic flame retardant system and its application effect in HIPS.

Research background: Magnesium hydroxide, as an environmentally friendly flame retardant, is favored for its low toxicity and high-efficiency flame retardant properties. Although red phosphorus has excellent flame retardant effects, it is usually used in combination with other materials due to its potential toxicity and stability issues. The addition of silicone rubber not only improves the impact resistance of HIPS, but also enhances the flame retardant effect of the material, achieving an overall improvement in performance.

Experimental principle:

· Flame retardant mechanism of magnesium hydroxide: Under high temperature conditions, magnesium hydroxide decomposes and absorbs heat to produce water vapor and magnesium oxide, which helps to reduce the material temperature and inhibit the combustion process.

· Flame retardant mechanism of red phosphorus: Red phosphorus generates phosphoric acid during pyrolysis to form a protective layer and isolate oxygen, thereby achieving the purpose of flame retardancy.

· Synergistic effect of silicone rubber: Silicone rubber forms a stable network structure at high temperature, improves the heat resistance and impact resistance of the material, and promotes the uniform dispersion of flame retardants in the HIPS matrix.

Experimental materials and methods:

· Experimental materials: High impact polystyrene (HIPS), magnesium hydroxide, red phosphorus and silicone rubber are used as the main materials, supplemented by coupling agents, dispersants and other additives.

· Experimental steps: Including pretreatment of raw materials, premixing of magnesium hydroxide and red phosphorus, melt blending of composite materials, uniform dispersion of silicone rubber, and curing and granulation of composite materials.

Performance test:

· Flame retardant performance test: The flame retardant performance of the composite material is evaluated by limiting oxygen index (LOI) and vertical burning test (UL-94).

· Thermal stability test: The thermal gravimetric analysis (TGA) is used to examine the thermal stability of the material.

· Mechanical properties test: The mechanical properties of the composite material were evaluated by tensile test, bending test, etc.

· Micromorphology observation: The microstructure of the material and the dispersion of the flame retardant were observed by scanning electron microscope (SEM).

Results and discussion:

· Flame retardant performance: The experimental results show that the addition of silicone rubber significantly improves the flame retardant performance of HIPS, the LOI value is improved, and the UL-94 test reaches V-0 level.

· Mechanical properties: The addition of silicone rubber improves the impact resistance of the composite material while maintaining good tensile and bending strength.

· Micromorphology: SEM observation shows that silicone rubber promotes the uniform dispersion of flame retardants in the HIPS matrix and reduces agglomeration.

Process optimization:

· Adjustment of flame retardant ratio: By optimizing the ratio of magnesium hydroxide and red phosphorus, the flame retardant performance of the composite material is maximized.

· Silicone rubber addition: The right amount of silicone rubber can improve the impact resistance of the composite material, but excessive performance degradation should be avoided.

· Optimization of extrusion conditions: Appropriate extrusion temperature and screw speed can help improve the dispersion of flame retardants, thereby improving the flame retardant effect.

The synergistic effect of silicone rubber significantly improves the flame retardant and mechanical properties of magnesium hydroxide and red phosphorus flame retardant HIPS composite materials. By optimizing process parameters, flame retardant HIPS materials with excellent comprehensive properties were prepared, providing new possibilities for the application expansion of HIPS.