FR additives for flexible PVC wire and cable insulation, including low-smoke alternatives with FL-ZHS zinc hydroxystannate.
Wire and cable insulation compounds must meet flame spread (IEC 60332, UL 1685) and increasingly, smoke density and toxicity limits (IEC 61034, NBS smoke chamber, EN 45545 for rail). ATO has historically been the standard synergist for halogenated W&C compounds, but IARC Group 2B classification and current supply constraints are driving specification reviews. FL-ZHS (zinc hydroxystannate) is specifically recommended for flexible PVC W&C applications. It provides superior smoke suppression and lower CO generation compared to ATO at comparable loadings, while meeting the same primary flame retardancy requirements. For a full analysis of the current ATO supply situation and zinc alternative qualification process, see our ATO Supply Disruption Brief and Zinc Synergist Substitution Guide.
In the U.S. market, wire and cable compounds must also meet UL 44 (thermoset-insulated wires), UL 83 (thermoplastic-insulated wires), and for transit applications, NFPA 130 smoke and flame requirements. FL-ZHS is recommended as the primary synergist evaluation for any W&C compound where smoke density reduction is a specification requirement alongside primary flame performance.
| Product | Application Role | Details |
|---|---|---|
| TCPP | Liquid FR for flexible PVC insulation | Details → |
| TDCPP | Higher-efficiency liquid FR for PVC compounds | Details → |
| FL-ZHS | Zinc hydroxystannate: primary low-smoke W&C synergist | Details → |
| FL-ZS | Zinc stannate synergist for PVC and rubber | Details → |
| FL-ZB | Zinc borate: multifunctional, afterglow suppression | Details → |
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LSZH cable is the fastest-growing compound segment in the U.S. wire and cable market, driven by NEC 2023 requirements in commercial buildings, NFPA 130 for transit applications, and data center riser/plenum specifications. LSZH formulations eliminate halogenated components entirely, requiring FR systems built around phosphorus, nitrogen, and mineral-based additives.
FL-ZB (zinc borate, CAS 138265-88-0) is the recommended low smoke zero halogen flame retardant synergist for LSZH cable compounds. As a U.S.-supplied LSZH FR additive, FL-ZB works in combination with ATH or MDH primary FRs to deliver smoke suppression, afterglow control, and char promotion without halogen contribution. For compounders qualifying a zinc borate LSZH compound for NEC 2023 or NFPA 130 compliance, evaluation quantities are available on request. FL-ZB product page →