Magnesium hydroxide is a typical inorganic halogen-free flame retardant applied for PVC, PP and other polyolefin materials. Its flame retardancy relies on multi-stage physical and chemical synergistic effects, without releasing toxic halogen-containing fumes during combustion. The detailed working principles are as follows:
1. Endothermic Decomposition Cooling Effect
When the temperature reaches approximately 340°C, magnesium hydroxide triggers thermal decomposition reaction:
\\(\\boldsymbol{Mg(OH)_2 \\rightarrow MgO + H_2O(g) – Heat}\\)
The reaction strongly absorbs massive heat from the combustion zone, lowering the surface temperature of PVC/PP substrates. It slows down thermal cracking of polymer chains and suppresses the generation of flammable volatile hydrocarbons, cutting off the fuel supply for combustion.
2. Water Vapor Dilution & Oxygen Isolation
Decomposition produces large amounts of water vapor. The water vapor dilutes combustible pyrolysis gas and oxygen concentration around the flame front. Meanwhile, water vapor forms an inert gaseous atmosphere, hindering the continuous oxidation reaction required for sustained burning.
3. Formation of Protective Barrier Layer
The solid product magnesium oxide (MgO) generated after dehydration deposits on the surface of burning PVC/PP, forming a dense, heat-resistant ceramic-like isolation layer. This compact barrier blocks heat transfer from external flame into the internal polymer matrix. It also prevents flammable decomposition gas from escaping outward and isolates oxygen contact with the base material, terminating flame propagation.
4. Smoke Suppression Effect
Unlike halogen flame retardants that generate heavy toxic smoke, magnesium hydroxide effectively reduces smoke density. The MgO layer adsorbs carbon soot particles produced by polymer incomplete combustion, achieving excellent low-smoke performance.
Supplementary Note for This 92% Whiteness Grade
This industrial-grade magnesium hydroxide with 92% whiteness usually undergoes surface modification. Improved compatibility with PVC and PP ensures uniform dispersion inside polymers. Even distribution enables consistent exertion of the above four flame-retardant mechanisms throughout materials such as plastic pipes, profiles and cable materials, avoiding local combustion defects.
Post time: Aug-17-2026