Brucite (Magnesium Hydroxide)

Brucite is a naturally occurring mineral form of magnesium hydroxide (Mg(OH)₂), crystallising in the trigonal system as soft, platelet-shaped particles with a characteristic pearly to vitreous lustre. It is sourced primarily from ultramafic and metamorphic geological formations, with commercially significant deposits located in China, Turkey, and Australia. The mineral is processed by selective mining, crushing, grinding, and classification to produce industrial-grade powders suitable for use as a flame retardant filler in polymer systems.

The fire retardant mechanism of brucite is endothermic dehydration. When heated, magnesium hydroxide decomposes to release water vapour and form magnesium oxide (MgO). This reaction absorbs approximately 1300 kJ/kg of heat energy, cooling the burning substrate and slowing the rate of thermal degradation. The water vapour released, approximately 31% by weight of the original mineral, dilutes combustible gases and oxygen in the flame zone. The residual MgO forms a thermally stable, electricite insulating char layer on the surface of the substrate, providing an additional barrier to heat transfer and flame propagation.

A key distinction between brucite and alumina trihydrate (ATH), the other principal mineral flame retardant, is decomposition temperature. Brucite begins to decompose at approximately 330°C, compared with approximately 200°C for ATH. This higher thermal stability makes brucite the preferred mineral flame retardant for polymer systems that require processing temperatures above the decomposition threshold of ATH, including polypropylene, polyamide, and certain engineering thermoplastics where compounding temperatures routinely exceed 250°C.

Brucite is classified as a halogen-free flame retardant (HFFR) and produces no toxic or corrosive by-products during combustion. It is available in standard, fine, and ultra-fine grades, with surface-treated variants using stearic acid or silane coupling agents to improve compatibility with non-polar polymer matrices. ROCC Global sources brucite from established mining and processing operations in Asia Pacific, Turkey, and Europe, with quality verification including particle size analysis, thermal analysis (TGA/DSC), and chemical composition by XRF.

Brucite is used as a halogen-free flame retardant and smoke suppressant in polymer compounds where fire safety performance is required without halogenated additives, and where processing temperatures exceed the practical limit of alumina trihydrate. Its primary application is in wire and cable compounds, particularly low-smoke zero-halogen (LSZH) formulations based on polyolefin and EVA matrices, where it provides effective flame retardancy, low smoke density, and low toxicity in compliance with international cable standards including IEC 60332 and EN 50399. The higher decomposition temperature of brucite compared with ATH allows it to survive the compounding and extrusion temperatures used in polypropylene-based cable insulation and sheathing without premature dehydration, which would otherwise cause porosity and loss of mechanical properties in the finished cable. In engineering thermoplastics including polyamide and polypropylene compounds for electrical enclosures, connectors, and automotive components, brucite provides flame retardancy at the elevated processing temperatures these polymers require. In rubber compounds for conveyor belts, seals, and industrial hoses, it contributes halogen-free flame retardancy with good retention of mechanical properties. Surface-treated grades are preferred in demanding polymer applications to ensure adequate dispersion at the high filler loadings typically required, minimising the impact on tensile strength and elongation at break.