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T-9 (Stannous Octoate, Tin(II) 2-Ethylhexanoate, CAS 301-10-0): Divalent Tin Catalyst for PU Foam and Skin-Contact Silicone
SEMITECH supplies T-9 at ≥95% active content (Sn ≈28%) — a divalent Sn(II) carboxylate that acts as the gel catalyst in flexible polyurethane foam and as the lower-toxicity tin catalyst for dental, prosthetic, and skin-contact RTV silicones where DBTDL would fail REACH downstream-use review. 5 kg / 25 kg HDPE jerrycans, 2–4 week ex-China lead time.
Contents
| 301-10-0 | ≥95% | ~28% |
|---|---|---|
| CAS number | Active content | Sn content |
Chemistry & Specifications
Divalent tin(II) bis(2-ethylhexanoate); MW 405.1; clear yellow viscous liquid; air- and moisture-sensitive.
T-9 (CAS 301-10-0) — MW 405.1, density 1.25 g/cm³, viscosity 250–400 cP. SEMITECH supplies at ≥95% active, Sn 27.5–28.5% (ICP-OES), water ≤0.2%, acid value 5–15 mg KOH/g. The divalent Sn(II) state oxidises to Sn(IV) on air exposure (brown-black precipitate = catalyst death). Sn(II) species are not subject to REACH organotin Annex XVII restrictions, making T-9 preferred for skin- and food-contact applications.
Cure Mechanism: PU Foam Gel Catalysis and Silicone Condensation
Catalyses urethane (NCO+OH) formation in flexible PU foam and condensation cure in dental/skin-contact RTV.
In PU foam, T-9 selectively catalyses the urethane gel reaction over the blowing reaction. In RTV silicone, it catalyses silanol-alkoxysilane condensation at substantially lower activity than DBTDL — tack-free times 90–180 min at 0.30% loading.
- Loading 0.10–0.30 phr — flexible slab-stock and moulded PU foam (mattress, seating, automotive)
- Loading 0.05–0.20 phr — semi-rigid integral-skin foam, microcellular elastomer
- Loading 0.20–0.50% — RTV silicone for dental impression, skin-contact prosthetics
- Loading 0.10–0.40% — neutral-cure RTV-1 for medical-device assembly
Like all tin catalysts, T-9 poisons platinum addition-cure systems; cross-contamination must be eliminated on shared equipment.
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Applications & Formulation Guidance
Flexible PU foam (largest), dental and prosthetic silicone, skin-contact RTV, lower-toxicity replacement for DBTDL.
Flexible PU foam (~80% of global T-9 demand) — slab-stock at 0.15–0.25 phr, moulded automotive at 0.20–0.40 phr, integral-skin at 0.10–0.20 phr. Dental impression silicone — T-9 at 0.30–0.50%, lower toxicity required for oral cavity use. Prosthetic/cosmetic silicone — 0.20–0.60% in low-viscosity RTV. Medical device assembly — T-9 at 0.10–0.30% paired with alkoxysilane crosslinker.
Procurement, Storage and Quality Control
Mandatory nitrogen blanket; CoA per shipment; 5 kg / 25 kg HDPE; 9-month shelf life sealed.
CoA per batch: Sn assay (27.5–28.5%), active content (≥95%), water (≤0.2%), acid value, viscosity, APHA colour. MOQ 5 kg sample, 25 kg production. Lead time 1–2 weeks Asia, 4–6 weeks Europe/North America. Mandatory: store sealed under nitrogen below 25°C; re-blanket after every draw; consume opened drums within 30 days. Shelf life 9 months (vs 12 months for Sn(IV) grades). T-9 is REACH-registered; Sn(II) species exempt from dialkyltin(IV) Annex XVII restrictions.
T-9 Specification Sheet
SEMITECH stocked grade; CoA per batch.
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Stannous octoate / Tin(II) 2-ethylhexanoate | — |
| CAS number | 301-10-0 | — |
| Molecular formula | Sn(C₈H₁₅O₂)₂ | — |
| Molecular weight | 405.1 g/mol | — |
| Active content | ≥95% | Iodine titration |
| Tin (Sn) content | 27.5–28.5% | ICP-OES |
| Appearance | Clear pale-yellow viscous liquid | Visual |
| Density (20°C) | 1.24–1.26 g/cm³ | ASTM D1475 |
| Viscosity (25°C) | 250–400 cP | Brookfield |
| Water content | ≤0.2% | Karl Fischer |
| Acid value | 5–15 mg KOH/g | ASTM D974 |
| APHA colour | ≤200 | ASTM D1209 |
| Solubility | Soluble in plasticisers, esters; insoluble in water | — |
| Packaging | 5 kg / 25 kg HDPE under nitrogen | — |
| Shelf life | 9 months sealed below 25°C | — |
FAQ
+Why does my T-9 turn dark brown after a few weeks?
Brown-to-black discolouration signals Sn(II) → Sn(IV) oxidation. The catalyst loses 30–60% activity once visible. Dispose and prevent recurrence by re-blanketing with nitrogen after every draw, consuming within 30 days.
+How much T-9 for a flexible PU mattress slab-stock?
Standard 30 kg/m³ density uses T-9 at 0.18–0.22 phr paired with DABCO 33LV at 0.10–0.14 phr. Higher density (45 kg/m³) seating: 0.25–0.30 phr.
+Is T-9 acceptable for dental impression silicone under EU MDR?
Yes. T-9 is the standard catalyst for condensation-cure dental impression silicone, accepted under EU MDR Class IIa. Sn(II) falls outside REACH Annex XVII organotin restrictions.