Flame Retardant
Magnesium Hydroxide Flame Retardant (MDH)
High-Purity Synthetic Mg(OH)₂ for Halogen-Free Compounds
As a magnesium hydroxide flame retardant supplier, Sychem offers synthetic Magnesium Hydroxide (MDH) — a fatty-acid-coated, ultra-fine mineral flame retardant filler engineered for halogen-free polymer compounds. With ≥98% purity, sub-2 μm median particle size, and a high decomposition onset of 340 °C, our MDH delivers reliable smoke suppression and char promotion across wire & cable, EV battery components, and engineering thermoplastics — the workhorse mineral retardant of choice for high-loading, cost-sensitive halogen-free formulations.
Headline Performance Indicators
The four numbers that compounders care about most
Why Magnesium Hydroxide
Three engineering reasons MDH remains the dominant mineral flame retardant in halogen-free polymer compounds worldwide
Heat Absorption + Water Release
At 340 °C, Mg(OH)₂ decomposes endothermically into MgO and H₂O — absorbing heat from the flame front while releasing water vapor that dilutes combustible gases. The high decomposition onset enables compounding with engineering thermoplastics that mineral retardants like ATH cannot survive.
Lower Smoke, Zero Toxic Acids
The MgO residue forms a protective ceramic layer that suppresses smoke generation and traps soot — outperforming halogen / antimony systems on smoke density and toxicity. Critical for transit, marine, and indoor cable applications subject to IEC 61034 and EN 45545.
High-Loading Workhorse
Fatty-acid surface coating enables loadings of 50–65 wt% with retained mechanical performance. Pairs naturally with Sychem’s HF-80 / HF-90 phosphorus systems for synergistic char + endothermic action — the standard halogen-free wire & cable formula.
Synthetic Mg(OH)₂ — Key Specifications
Fatty-acid-coated synthetic magnesium hydroxide · CAS No. 1309-42-8
The full technical data sheet, with composition, particle size distribution, bulk density, moisture, whiteness and trace impurity limits, is sent by email on request together with the SDS. Tell us your polymer and target flame rating, and we will send the TDS for the grade that fits. A COA accompanies every shipment.
Where Synthetic MDH Is Used
High-loading mineral flame retardant for halogen-free polymer compounds
MDH vs ATH — When to Specify Magnesium Hydroxide
Both are mineral flame retardants — but the 340 °C decomposition onset of MDH unlocks polymer systems that ATH cannot serve
Dosage Guidelines & Processing
Recommended starting points — final dosage depends on substrate, target rating, and co-additives
Safety, Handling & Compliance
Non-hazardous goods classification with full regulatory documentation
Hazard Classification
Classified as non-hazardous goods. No explosion hazard — environmentally friendly halogen-free flame retardant. No fire, no toxic gas evolution under normal handling conditions.
Handling Precautions
Dust may enter via inhalation, ingestion, or absorption through nose and mouth. Use standard dust mask, eye protection, and ventilation when handling. No special hazardous-goods storage or transport required.
Regulatory Documentation
Full documentation package available: SDS, TDS, COA, REACH registration, RoHS declaration, halogen-free declaration. Packaged in 25 kg bags or 1 ton FIBC bulk bags. Container-load shipping worldwide.
The Sychem Sourcing Advantage
Reliable mineral flame retardant supply from China, with the technical depth of a specialty distributor
Sample Synthetic MDH for Your Halogen-Free Compound
Tell us your polymer, target UL rating, and processing temperature — we will recommend the right MDH grade and confirm if synergy with HF-80 or HF-90 phosphorus systems can lower your total loading.
Request Sample & TDS →Your Magnesium Hydroxide Flame Retardant Supplier
SYCHEM TECH is a magnesium hydroxide flame retardant supplier based in Shenyang, China, offering high-purity (≥98%) synthetic, fatty-acid-coated MDH with sub-2 μm median particle size and a 340 °C decomposition onset for halogen-free wire and cable (LSZH), EV battery components, and engineering thermoplastics. As your formulation development partner, we match the right particle size, coating, and loading to your polymer and UL94 target, and can combine MDH with phosphorus systems to lower total loading. For background, see the overview of magnesium hydroxide.
Looking for a reliable magnesium hydroxide flame retardant with technical support? Tell us your polymer, target UL rating, and processing temperature, and our team will recommend an MDH grade and arrange samples. Explore the parent flame retardants range, our phosphorus-based flame retardants, and the full functional additives portfolio.
Further reading: Phosphorus vs MDH flame retardants: how magnesium hydroxide compares with phosphorus-based systems in mechanism, performance trade-offs and typical applications. Choosing between magnesium hydroxide and aluminium trihydrate? See MDH vs ATH.
Magnesium hydroxide FAQ
How does magnesium hydroxide flame retardant work?
Magnesium hydroxide (Mg(OH)₂, MDH) is a halogen-free mineral flame retardant. From about 340 °C it decomposes into magnesium oxide and water, absorbing heat and releasing water vapor that dilutes the flammable gases. The MgO residue forms a protective layer that suppresses smoke, and no corrosive or toxic acid gases are released. Its higher decomposition temperature is the main difference from ATH; see MDH vs ATH.
Is MDH suitable for EVA and PE LSZH cable compounds?
Yes. MDH is a standard filler for low-smoke zero-halogen (LSZH) insulation and sheathing based on EVA, PE and POE blends, usually at 55–65 wt%. Its 340 °C decomposition onset leaves a wide margin for high-temperature extrusion, where ATH can start to release water and cause voids. A fatty-acid-coated grade disperses better at high loading and keeps the melt easier to process.
Which MDH particle size should I choose for cable compounds?
Our standard synthetic grade has a D50 below 2 μm. Finer grades below 1 μm suit thin-wall insulation and help tensile strength and elongation; coarser grades of 1.5–3 μm lower melt viscosity at very high loadings. Custom particle sizes are available on request, so tell us your wall thickness, loading and extrusion line.
How can I keep elongation and tensile strength at high MDH loading?
Use a surface-treated MDH, add 0.5–1.5% silane or a maleic-anhydride-grafted compatibilizer, and feed the filler through a side feeder on a twin-screw extruder. MAH-grafted PE such as our SY-PX and SY-PZ compatibilizers bonds the polymer to the MDH surface, which helps elongation at break in EVA and PE cable compounds.
Which charring agents and synergists work with MDH?
Phosphorus-based systems are the most common partner: co-loading MDH with our HF-80 or HF-90 at an MDH-to-phosphorus ratio of about 3:1 to 5:1 adds char formation to the endothermic effect, so total filler can be reduced. Zinc borate and nanoclay are also used as synergists. See our phosphorus-based flame retardants.
What is the difference between synthetic and brucite-based MDH?
Brucite-based MDH is ground from natural mineral ore. It costs less but has coarser, less uniform particles and more impurities. Synthetic MDH is precipitated, with higher purity (≥98%), finer and more uniform particles and better whiteness, which helps mechanical properties and electrical performance in demanding cable and engineering-plastic compounds. SYCHEM TECH supplies synthetic MDH.
How is MDH shipped, and what support do you give from lab to production?
As a magnesium hydroxide flame retardant supplier, we ship in 25 kg bags or 1 tonne FIBC bulk bags, in full container loads to customers worldwide, with a COA for every batch. We email the TDS and SDS, send samples for lab trials, and help with loading, coupling agents and compounding settings when you scale up. Contact our team or write to info@sychemtech.com.