ATO supply is constrained. But qualifying an alternative requires understanding which zinc synergist works best in which substrate. This guide breaks it down by chemistry, mechanism, and application.
Three Zinc Synergists—How They Differ
FL-ZS, FL-ZHS, and FL-ZB are all inorganic zinc-based synergists, but they differ meaningfully in chemistry, mechanism, and best-fit application.
| Product | Chemistry | Smoke Suppression | Afterglow Suppression | Halogen-Free Compatible | Best Substrate |
|---|---|---|---|---|---|
| FL-ZS | Zinc stannate | Good | No | No | Rigid/flex PVC, polyolefins |
| FL-ZHS | Zinc hydroxystannate | Excellent | No | No | Flexible PVC, wire & cable |
| FL-ZB | Zinc borate | Good | Yes | Yes | Universal—incl. halogen-free |
How Zinc Synergists Work
ATO works primarily via a gas-phase mechanism—antimony halides form in the flame zone and scavenge radicals that propagate combustion. Zinc synergists work differently and in some cases more broadly:
- FL-ZS / FL-ZHS: Zinc tin compounds decompose at the polymer surface forming char and tin oxide, blocking heat transfer and oxygen access. Also gas-phase activity via ZnO/SnO₂ catalytic action.
- FL-ZB: Multiple mechanisms—boric acid melts to form a glassy char layer, ZnO promotes cross-linking, and water of crystallisation provides endothermic cooling. This multi-mechanism action is why FL-ZB uniquely suppresses afterglow.
Starting Point Loading Guidance
These are starting points for formulation work only. Full fire testing (UL 94, LOI, IEC 60332, etc.) is required to confirm compliance in your specific system.
| System | Typical ATO Baseline | FL-ZS / FL-ZHS Starting Point | FL-ZB Starting Point |
|---|---|---|---|
| Rigid PVC | 3–5 phr | 3–6 phr (1:1 to 1.2:1) | 3–5 phr |
| Flexible PVC (W&C) | 3–6 phr | FL-ZHS 4–8 phr preferred | 3–6 phr |
| Polyolefin (brominated) | 2–4 phr | 3–5 phr | 2–4 phr |
Request Evaluation Samples + TDS
We supply FL-ZS, FL-ZHS, and FL-ZB in evaluation quantities. Include your substrate, target fire standard, and current ATO loading in your RFQ.