Primary ATO alternative for flexible PVC wire and cable insulation. Superior smoke suppression for IEC 61034 and NBS smoke density compliance.
FL-ZHS is a zinc hydroxystannate (ZnSn(OH)₆) flame retardant synergist with superior smoke suppression compared to both ATO and FL-ZS. It is the primary Flamisol recommendation for flexible PVC wire and cable insulation compounds where IEC 61034 smoke density or NBS smoke chamber limits apply.
| Property | FL-ZHS Value |
|---|---|
| Chemical name | Zinc Hydroxystannate (ZnSn(OH)₆) |
| CAS No. | 12027-96-2 |
| Zinc content | ~28% |
| Tin content | ~39% |
| Form | White powder |
| Particle size (D50) | ~4–7 μm |
| Density | ~3.3 g/cm³ |
| Decomposition onset | Endothermic dehydration on heating (beneficial) |
| Water of crystallization | ~14% (released endothermically) |
| Halogen content | None |
| TSCA status | Listed |
| IARC classification | None (vs Group 2B for ATO) |
| Typical loading (partial ATO) | 3–5 phr in TDCPP/flexible PVC |
| Typical loading (full ATO replacement) | 5–8 phr |
| Packaging | 25 kg bags / 500 kg supersacks |
| U.S. lead time | Confirmed at quotation |
FL-ZHS has two mechanisms ATO lacks. First, the endothermic dehydration on heating absorbs heat from the combustion zone, reducing flame spread. Second, the hydrated structure provides enhanced solid-phase smoke suppression: ZnO and SnO₂ formed during decomposition catalyze char formation more effectively than anhydrous FL-ZS, resulting in measurably lower NBS smoke density and CO output in flexible PVC formulations.
In IEC 61034-compliant flexible PVC cable compounds, FL-ZHS typically delivers 20–35% lower smoke density vs ATO-only baselines at equivalent total synergist loading. This is the performance delta that allows specification compliance without increasing primary FR loading.
| Substrate | FL-ZHS | Notes |
|---|---|---|
| Flexible PVC wire & cable | ✓ Primary recommendation | Best smoke suppression for IEC 61034 and NBS smoke density compliance |
| Rigid PVC | ✓ Good | Use FL-ZS for higher-temperature processing where water release is undesirable |
| Flexible PVC films / sheeting | ✓ Good | Smoke density reduction benefit in conveyor belts, automotive interiors |
| Polyolefins | ⚠ Limited | Moisture sensitivity at processing temps; FL-ZS preferred for polyolefins |
| Halogen-free cable (LSZH) | ✗ Not suitable | Requires halogen to activate. Use FL-ZB for LSZH systems. |
FL-ZHS-M is the micronized grade of zinc hydroxystannate, milled to a finer particle size (D50 ≤ 2.0 µm, typical 1.5 µm) than standard FL-ZHS. The finer particle size is the point. It improves dispersion in the polymer, supports a smoother surface finish, and helps loading efficiency, which matters most in thin and demanding formats.
That makes FL-ZHS-M well suited to flexible PVC films, thin-gauge and calendered applications, and dispersions, where coarse particles can telegraph at the surface or disperse unevenly. In these systems the finer grade lets the same smoke-suppression and flame-retardant chemistry work where a standard particle size would be a compromise.
Like standard FL-ZHS, the micronized grade serves as a qualified antimony trioxide (ATO) alternative in low-smoke flexible PVC: as a partial replacement, a route to lower ATO loading, or a synergist in brominated systems. With ATO supply and pricing under ongoing pressure, FL-ZHS-M gives formulators of thin flexible PVC a way to qualify a second source. Substitution levels depend on the system and the fire standard and should be confirmed by application-specific fire testing (LOI, UL-94). You can compare FL-ZS, FL-ZHS and FL-ZB, review the ATO substitution guide, or see wire and cable applications. Flamisol supplies FL-ZHS-M, with TDS, SDS, and COA available on request, and DDP supply options.
Partial replacement: Evaluate FL-ZHS at 3–5 phr as a partial replacement for ATO in TDCPP/flexible PVC insulation compounds, maintaining existing primary FR loading.
Full replacement: Loadings of 5–8 phr reported in literature for IEC 61034-compliant smoke density. Formulation testing against target fire standard required. Evaluation quantities available →
FL-ZHS supplied DDP from a US-based supplier. SDS, TDS, TSCA compliance letter on request. DDP pricing within one business day.
Request FL-ZHS Pricing & TDSGuide to zinc-based FR synergists · FL-ZHS vs FL-ZS comparison
Provide your details and we will send the requested SDS, TDS, or CoA within 24 hours.
Zinc hydroxystannate (FL-ZHS) is used as a flame retardant synergist and smoke suppressant, most often in flexible PVC and wire and cable insulation and jacketing. It is valued in low-smoke applications because it suppresses smoke as well as supporting flame retardancy. It is typically used in lower-temperature systems because it releases bound water when heated.
Yes. FL-ZHS is used as a qualified alternative to antimony trioxide (ATO): as a partial replacement, a way to reduce ATO loading, or a synergist in brominated systems. Full ATO elimination is possible in specific systems but should be confirmed by application-specific fire testing. It is a relevant option given ongoing ATO supply pressure.
Yes. The micronized grade, FL-ZHS-M, has a finer particle size (D50 ≤ 2.0 µm, typical 1.5 µm) suited to flexible PVC films, thin-gauge applications, and dispersions where dispersion quality and surface finish matter. Flamisol supplies it, with TDS and SDS available on request.