MDH: production, applications, development

Extensive review of current and potential production routes, applications, functionalisation and fire safety benefits of MDH (magnesium di.hydroxide), a widely used PIN flame retardant.

This 50-page research analysis presents the different current industrial routes for production of MDH (mainly from mining or hydration of MgO) and possible future routes and options to reduce energy consumption, including recovery by precipitation from magnesium rich waste brines from e.g. desalination. Processes aim to optimise not only particle size but also surface area, pore size distribution, basicity.

The mechanisms of MDH in protecting from fire are explained: absorption of heat by endothermic decomposition and release of water vapour. MDH also contributes to stiffness, modulus and heat deflection in polymer compounds, and its basicity contributes to counter acid degradation.

Processes for optimising MDH’s fire safety effectiveness and polymer compatibility are presented. Particle size control is important: industrially today by milling or controlled precipitation, potentially in the future by microwave, ultrasound, microemulsions. The density of surface hydroxyl (OH) groups in MDH enable modification and functionalisation, to address polymer compatibility issues, improve dispersion, reduce hydrophilicity or improve fire performance (synergy with char forming or ceramifying substances), e.g. with organic silanes, fatty acid – metal soaps, maleic anhydride.

Application in a wide range of polymers is discussed, including relevant strategies for improving compatibility, mechanical and fire performance.

The review concludes that MDH is a robust, safe and sustainable PIN flame retardant, including for low-smoke applications, for polymers, wood, natural fibres, subject to appropriate compatibilsation and functionalisation, often in synergy with phosphorus and nitrogen PIN FRs to enable lower loadings or targeted fire safety performance.

“Investigation of Magnesium Hydroxide as a Halogen-Free Fire-Retardant Filler for Advanced Polymer-Based “, F. Ferrante et al., Composite Solutions: A Review Polymers 2026, 18(11), 1386. https://doi.org/10.3390/polym18111386

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