Layered Double Hydroxide (LDH) Nano Flame Retardant

Layered double hydroxides (LDH, general formula [M²⁺₁₋ₓM³⁺ₓ(OH)₂]ˣ⁺[Aⁿ⁻ₓ/ₙ·mH₂O], e.g., Mg-Al-LDH) are synthetic anionic clays with platelet thickness of 0.48 nm and aspect ratio of 50–200, incorporated into textile coatings or fiber matrices at 5–15 wt%. Thermal decomposition of LDH at 200–350°C releases CO₂ and H₂O endothermically (ΔH = 1,500–2,000 J/g), diluting flammable gases and cooling combustion zone. LDH at 10 wt% in EVA coating reduces pHRR by 45% (cone calorimeter) and increases TTI (time to ignition) by 25 seconds. Anion exchange capacity (200–400 meq/100g) enables intercalation of organic FR anions (borate, phosphate) for enhanced barrier effect. Synergy with intumescent systems at LDH:APP ratio 1:4 achieves LOI 32% and UL-94 V-0 rating in cotton fabric coating at total loading of 15% owf — 40% lower than APP alone.