Zr(IV) with sulfonyl ester ligand (R-SO₂-O-Zr); clear amber liquid; 220°C thermal stability.

SZ-44 is a sulfonyl-zirconate — a hybrid Zr(IV) compound with one neopentyl-glycolate ligand for thermal stability and one sulfonyl ester ligand (R-SO₂-O-Zr where R is typically a long-chain alkyl) for filler-anchoring and char-formation contribution. The sulfonyl ester provides a different anchoring chemistry than the pyrophosphate of SZ-12: sulfonyl-O-Zr-O-filler bonds form preferentially on basic filler surfaces (MgO from MDH dehydration; ZnO; carbonate-rich CaCO₃) rather than the acidic Al(OH)₃ surface of ATH. SEMITECH supplies SZ-44 as a clear amber liquid at ≥80% active content with ZrO₂ assay 14.0–15.0%, sulphur content 4.5–5.5%, water content ≤0.2% by Karl Fischer.

SZ-44 is functionally equivalent to Kenrich NZ-44 — both products use the same neoalkoxy-sulfonyl chemistry. SEMITECH supply pricing: ex-Zhejiang spot CNY 70,000–85,000/MT (USD 9.8–11.9/kg) vs Kenrich NZ-44 distributor pricing North America USD 19–24/kg landed — 40–55% landed-cost discount. The sulphur content provides a unique mechanistic advantage in flame-retardant compound LOI testing: sulphur-bearing fragments released during thermal decomposition contribute to the gas-phase free-radical scavenging chemistry (similar in mechanism to sulphur-bearing flame retardants), providing an additional 1–2 LOI units uplift versus phosphato zirconate alternatives in EVA-MDH systems where MgO surface chemistry favours sulfonyl coupling over phosphate coupling.

Sulfonyl ester binds to MgO/MDH surface via Zr-O-S-O-Mg linkage; sulphur contribution to gas-phase flame chemistry.

In MDH-filled and high-LOI flame-retardant compounds, SZ-44 couples by reaction of the sulfonyl ester ligand with surface –OH groups on basic filler particles. The sulfonyl-O-Zr bond hydrolyses with surface hydroxyl, releasing the sulfonate group and forming a Zr-O-Mg or Zr-O-Ca surface bond on the filler particle. The remaining alkyl groups extend into the polymer matrix providing entanglement coupling to EVA, polyolefin, or matrix chains. The freed sulfonate group contributes to the char-forming chemistry during compound burn — sulphur radicals scavenge propagating gas-phase radicals (similar mechanism to sulphur-bearing flame retardants), reducing the rate of further pyrolysis and improving LOI rating.

• 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

The 220°C thermal stability ceiling of SZ-44 is slightly lower than the 240°C ceiling of SZ-12 (the sulfonyl ester is more thermally labile than the pyrophosphate ester at high temperature), making SZ-44 optimal for compounds processed below 220°C — EVA-MDH cable jackets (220°C), polyolefin-MDH compounds (200°C), and intumescent coatings (RT to 100°C). For higher-temperature engineering plastic compounding (PA66 at 260°C, PBT at 245°C), specify SZ-12 phosphato-zirconate which retains structural integrity to 240°C.

EVA-MDH HFFR cable jackets (largest), intumescent coating modifier, polyolefin-MDH compounds, fire-rated mastic.

EVA-MDH high-LOI HFFR cable jacket compounds are the largest single application for SZ-44 — premium-tier building wire (LSZH 0H specification), railway and metro cable, marine and offshore cable, and transit-rated automotive battery cable. Standard high-LOI formulation: EVA matrix at 35–40%, MDH filler at 55–60%, SZ-44 at 0.7–1.2 phr on filler, antioxidants and processing aids at 1–3%. Compounded at 200–220°C, the SZ-44 provides effective MgO surface coupling (where SZ-12 phosphate coupling is sub-optimal due to MgO’s basic surface chemistry preferring sulfonyl over phosphate anchoring) and additional sulphur-radical chemistry contribution to the gas-phase combustion suppression. Typical: LOI 35+ at 60% MDH loading with SZ-44 vs LOI 33–34 with SZ-12 at the same conditions.

Intumescent coating modifier for fire-rated paint, mastic, and structural fire-protection systems uses SZ-44 at 0.7–1.2% on resin solids to enhance the char-formation chemistry. Standard intumescent coating formulation: ammonium polyphosphate (APP) char former + pentaerythritol (PER) carbon source + melamine spumific + acrylic or alkyd binder + SZ-44 — gives improved char volume expansion (50–80×) and char rigidity vs unmodified intumescent paint. Polyolefin-MDH and dolomite-filled fire-resistant compounds for indoor cabling, transit interior parts, and electrical equipment housings use SZ-44 at 0.5–1.0 phr to provide both coupling effectiveness and incremental LOI uplift. Avoid SZ-44 in ATH-only systems — for ATH-Al(OH)₃ filler, the acidic Al-OH surface chemistry favours phosphate coupling (SZ-12 NZ-12) over sulfonyl coupling; specify SZ-12 for ATH systems.

CoA per shipment; 25 kg HDPE under N₂; 12-month sealed shelf life; nitrogen-blanket discipline required.

SEMITECH issues a CoA on every batch with: ZrO₂ assay (gravimetric ignition, target 14.0–15.0%), sulphur content (combustion analysis, target 4.5–5.5%), active content (titration, target ≥80%), water content (Karl Fischer, target ≤0.2%), APHA colour, density, and viscosity. Standard packing 25 kg HDPE jerrycans under dry nitrogen blanket; 200 kg lined steel drums for bulk HFFR cable compound producers. MOQ 25 kg per grade. Lead time 1–2 weeks ex-Zhejiang to Asia gateway ports for stocked grade, 4–6 weeks to Europe and North America after sea freight.

Storage: nitrogen-blanket sealed below 25°C; re-blanket headspace after every draw; consume opened drums within 30 days; shelf life 12 months sealed. The sulfonyl ester ligand is slightly more hydrolytically resistant than simple alkoxide but still sensitive to bulk water exposure. Cost positioning: SZ-44 Q1 2026 ex-Zhejiang spot CNY 70,000–85,000/MT (USD 9.8–11.9/kg); Kenrich NZ-44 distributor pricing North America USD 19–24/kg landed, Europe USD 22–28/kg — 40–55% landed-cost discount for SEMITECH supply. Bulk orders ≥1 t qualify for volume discount programme. Health: skin and eye irritant; flammable solvent (typically n-butanol or n-propanol carrier) flash point 35–40°C. Standard PPE — nitrile gloves, splash goggles. SDS in EU/GHS format issued with every shipment.

SZ-44 is the high-LOI sulfonyl-zirconate — Kenrich NZ-44 equivalent at 40–55% landed-cost discount. Optimal for EVA-MDH HFFR cable jackets and intumescent coating modifiers where MgO surface chemistry favours sulfonyl over phosphate coupling. LOI uplift 1–2 units vs SZ-12 phosphate at equivalent loading in MDH systems. 220°C thermal stability — for >220°C PA66/PBT/PPS specify SZ-12.

SEMITECH stocked grade; CoA per batch.