LDH (layered double hydroxide) is a mineral fire retardant built from stacked metal-hydroxide layers that store water and anions. On heating it absorbs heat, releases cooling water vapour, forms a protective char and mineral shield, and suppresses smoke — all without any halogens.
If you've been researching fire retardant coatings, you've probably run into a wall of jargon — intumescent, halogenated, char formation, gas-phase inhibition. LDH fire retardant is one of the newer, safer options, and the good news is that the idea behind it is refreshingly simple. This guide explains what LDH is and how it stops fire, without the chemistry degree.
What does LDH stand for?
LDH stands for Layered Double Hydroxide. Picture a stack of thin mineral sheets, like pages in a book. Each sheet is made of metal and hydroxide (that's the "hydroxide" part). Between the sheets sit two things that matter enormously for fire safety: water molecules and carbonate ions.
That layered structure is the whole trick. LDH is essentially a mineral sponge that holds water and gas-forming compounds locked away until heat releases them.
How LDH fire retardant works
When fire meets an LDH-coated surface, three things happen almost at once:
- It absorbs heat. Breaking down the hydroxide layers is an endothermic reaction — it soaks up energy from the flame, cooling the surface and delaying ignition.
- It releases water vapour. The stored water escapes as steam, diluting the flammable gases and oxygen a fire needs to keep going.
- It leaves a mineral shield. What's left behind is a stable, non-combustible residue that insulates the material underneath from further heat.
Compare that to old-school halogenated retardants, which interfere with the fire's chemistry and can release toxic, corrosive smoke as they do it. LDH works physically — cool, dilute, shield — and gives off nothing worse than water vapour.
In lab testing, Aeon Core's LDH retained 82.36% of its mass even at 899°C — proof that most of the coating stays behind as a protective heat shield rather than burning away.
What makes LDH different from ordinary fire retardants
Most fire retardants do one thing. LDH is unusual because it works on several fronts at once, which is why researchers describe it as a multifunctional flame retardant:
- It suppresses smoke. As it breaks down, the layered structure and the char it forms trap smoke and toxic gases. That's the opposite of halogenated retardants, which often make smoke worse — and smoke is what actually harms people in a fire.
- It builds a real barrier. LDH catalyses a compact, continuous char and leaves behind a heat-resistant metal-oxide layer that physically shields the surface underneath.
- It's paint-friendly. LDH is naturally alkaline (around pH 10) — the same range as water-based paint — so it can be blended straight into paint and stay stable, instead of curdling it the way acidic additives do. See how it works in paint.
- It adds corrosion protection. The same anion-exchanging layers that fight fire also mop up corrosive ions, a well-documented bonus of LDH coatings.
Why "halogen-free" is the headline
Many traditional flame retardants rely on bromine or chlorine (halogens). They work, but when they burn they can produce corrosive gases and dioxins — and several are now restricted worldwide. Because LDH contains no halogens, it sidesteps that entire problem. That's why it's increasingly the choice for indoor spaces, furniture, textiles and packaging. Read more in our guide to halogen-free fire retardants.
Where LDH coatings are used
Because LDH can be formulated as a thin, clear, water-based coating, it suits materials that thick intumescent paints would ruin: wood, plywood, MDF, paper, cardboard, fabric and bamboo. It's ideal for interiors where you want fire protection without changing how something looks.
Is LDH proven? What the science says
LDH flame retardancy isn't a marketing invention — it's an active, well-documented area of peer-reviewed materials science, including work on halogen-free LDH coatings for wood and polymers. What that research consistently describes — endothermic water release, catalytic char formation, a refractory mineral barrier and smoke suppression — is exactly the behaviour we measure in our own lab characterization and burn tests. The mechanism is established science; Aeon Core's contribution is turning it into a practical, paint-friendly additive you can actually buy in India.
How Aeon Core uses LDH
Aeon Core LDH Gel is India's first fire retardant coating built on this technology. It's a nano-scale LDH colloid (particles around 285 nm) that penetrates porous surfaces and dries clear. We've published the full XRD, TGA, FTIR and DLS test data so you can see the science for yourself.