SZ-44 (Sulfonyl-Zirconate, Kenrich NZ-44 Equivalent): The High-LOI Zirconate for EVA-MDH and HFFR Cable Jacket Compounds
SEMITECH SZ-44 is the sulfonyl-functionalised zirconate — Kenrich NZ-44 equivalent — for high-LOI flame-retardant compounds where the sulfonyl ligand contributes sulphur to gas-phase radical scavenging during burn. Used at 0.5–1.5 phr in EVA-MDH HFFR cable jackets and intumescent coating modifiers. 220°C thermal stability, 25 kg HDPE.
Contents
| NZ-44 | 0.5–1.5 phr | 220°C |
|---|---|---|
| Kenrich equivalent | Typical loading | Thermal stability |
Chemistry & Specifications
Zr(IV) with sulfonyl ester ligand (R-SO₂-O-Zr); clear amber liquid; 220°C thermal stability.
SZ-44 has neopentyl-glycolate for thermal stability and a sulfonyl ester for filler-anchoring on basic surfaces (MgO from MDH, ZnO, CaCO₃). SEMITECH supplies at ≥80% active, ZrO₂ 14.0–15.0%, sulphur 4.5–5.5%, water ≤0.2%.
Pricing: CNY 70,000–85,000/MT vs Kenrich NZ-44 at USD 19–24/kg — 40–55% discount. Sulphur fragments provide 1–2 additional LOI units vs phosphato zirconate in EVA-MDH systems.
Coupling Mechanism: Sulfonyl-Zr Anchor on Basic Filler Surfaces + Char Formation
Sulfonyl ester binds to MgO/MDH surface via Zr-O-S-O-Mg linkage; sulphur contribution to gas-phase flame chemistry.
- Loading 0.5–1.0 phr — standard EVA-MDH HFFR cable jacket compounds
- Loading 1.0–1.5 phr — high-LOI EVA-MDH formulations (LOI 35+ at 60% MDH)
- Loading 0.7–1.2 phr — intumescent coating modifier for fire-rated paint and mastic
- Loading 0.5–1.0 phr — talc-filled and dolomite-filled fire-resistant compounds
220°C ceiling is slightly lower than SZ-12's 240°C — optimal for EVA-MDH (220°C) and polyolefin-MDH (200°C). For PA66/PBT/PPS above 220°C, specify SZ-12.
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Applications & Formulation Guidance
EVA-MDH HFFR cable jackets (largest), intumescent coating modifier, polyolefin-MDH compounds, fire-rated mastic.
EVA-MDH high-LOI HFFR cable jackets are the largest application — building wire, railway/metro cable, marine cable. Standard: EVA 35–40%, MDH 55–60%, SZ-44 0.7–1.2 phr. LOI 35+ at 60% MDH vs LOI 33–34 with SZ-12 phosphate, because MgO's basic surface favours sulfonyl coupling.
Intumescent coating modifier at 0.7–1.2% enhances char volume expansion (50–80×) and rigidity. Avoid SZ-44 in ATH-only systems — ATH's acidic Al-OH surface favours phosphate coupling (SZ-12).
Procurement, Storage and Quality Control
CoA per shipment; 25 kg HDPE under N₂; 12-month sealed shelf life; nitrogen-blanket discipline required.
Standard packing 25 kg HDPE under N₂; 200 kg drums for bulk. MOQ 25 kg. Lead time 1–2 weeks to Asia, 4–6 weeks to Europe/North America. Store sealed under N₂ below 25°C; consume within 30 days of opening. Flash point 35–40°C (solvent carrier).
SZ-44 Specification Sheet
SEMITECH stocked grade; CoA per batch.
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Neoalkoxy sulfonyl-zirconate | — |
| Synonyms | NZ-44 equivalent / sulfonyl-Zr / Zr(OR)₂(OSO₂R)₂ | — |
| Form | ≥80% in n-propanol / n-butanol carrier | — |
| ZrO₂ content | 14.0–15.0% | Gravimetric ignition |
| Sulphur content | 4.5–5.5% | Combustion analysis |
| Active content | ≥80% | Titration |
| Appearance | Clear amber liquid | Visual |
| Density (20°C) | 1.05–1.07 g/cm³ | ASTM D1475 |
| Viscosity (25°C) | 50–80 cP | Brookfield |
| Water content | ≤0.2% | Karl Fischer |
| APHA colour | ≤350 | ASTM D1209 |
| Flash point | 35–40°C (solvent, closed cup) | ASTM D93 |
| Thermal stability | 220°C continuous | — |
| Solubility | n-propanol, n-butanol, toluene; reacts with water | — |
| Packaging | 25 kg HDPE under N₂ / 200 kg lined steel drum | — |
| Shelf life | 12 months sealed below 25°C under N₂ | — |
FAQ
+When should I specify SZ-44 instead of SZ-12 in my HFFR cable compound?
SZ-44 when: (1) filler is MDH (basic MgO surface favours sulfonyl); (2) target LOI 35+ needing sulphur radical contribution; (3) process temperature below 220°C. SZ-12 when: filler is ATH, process above 220°C, or phosphorus char-forming is preferred.
+Will the sulphur content in SZ-44 cause discolouration in white cable jackets?
Slight risk with incompatible stabilisers. Use calcium-zinc or organic stabilisers rather than lead-based. Limit to ≤0.7 phr for colour-critical formulations and confirm with colour-chip trials.
+Can I use SZ-44 in food-contact or medical-device fire-resistant compounds?
No — no SEMITECH zirconate grade is currently approved for direct food-contact or medical-device applications. For food-contact fire-resistant compounds, specify silane-based coupling agents with FDA compliance.