Divalent tin(II) bis(2-ethylhexanoate); MW 405.1; clear yellow viscous liquid; air- and moisture-sensitive.

T-9 — stannous octoate, also written as tin(II) 2-ethylhexanoate or stannous 2-ethylhexanoate, CAS 301-10-0 — is a divalent tin compound formed from tin(II) oxide and 2-ethylhexanoic acid. Molecular formula C₁₆H₃₀O₄Sn, molecular weight 405.1 g/mol, density 1.25 g/cm³ at 20°C, viscosity 250–400 cP at 25°C. SEMITECH supplies T-9 as a clear yellow viscous liquid at ≥95% active content with tin assay 27.5–28.5% by ICP-OES, water content ≤0.2% by Karl Fischer, and acid value 5–15 mg KOH/g (free 2-ethylhexanoic acid).

The Sn(II) divalent state is what differentiates T-9 from DBTDL and DOTL (both Sn(IV) tetravalent). Divalent tin is more reactive and air-sensitive — T-9 oxidises to Sn(IV) on prolonged air exposure, forming a brown-black tin oxide precipitate that signals catalyst death. Storage under nitrogen blanket is mandatory beyond initial sealed shelf life. The toxicology profile differs meaningfully: Sn(II) species are not subject to the REACH organotin Annex XVII restrictions that apply to dialkyltin(IV) compounds, making T-9 the preferred catalyst for skin-contact and food-contact silicone applications.

Catalyses urethane (NCO+OH) formation in flexible PU foam and condensation cure in dental/skin-contact RTV.

In flexible polyurethane foam, T-9 selectively catalyses the urethane (isocyanate + polyol) gel reaction over the urea (isocyanate + water) blowing reaction — the inverse of amine catalysts. A typical flexible slab-stock formulation pairs T-9 at 0.10–0.30 phr with an amine blowing catalyst (DABCO 33LV, A-1) at 0.05–0.15 phr; the amine kicks off CO₂ generation while T-9 builds polymer network strength, the timing balance between the two determines cell structure (open-cell vs partially closed) and density.

• 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 moulded 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

In condensation-cure RTV silicone, T-9 catalyses the same silanol-alkoxysilane condensation as DBTDL/DOTL but at substantially lower activity — typical tack-free times are 90–180 minutes at 23°C and 50% RH at 0.30% loading. The slow cure profile is acceptable for dental impression (the operator wants 90+ seconds working time) and prosthetic mould-making (where deep sections need uniform through-cure). Like all tin catalysts, T-9 poisons platinum addition-cure systems; cross-contamination must be eliminated on shared equipment.

Flexible PU foam (largest), dental and prosthetic silicone, skin-contact RTV, lower-toxicity replacement for DBTDL.

Flexible polyurethane foam is the dominant application, accounting for ~80% of global T-9 demand. Slab-stock continuous foam lines for mattress and furniture cushion use T-9 at 0.15–0.25 phr; moulded automotive seating and headliner foam at 0.20–0.40 phr; integral-skin foam for steering wheels and shoe soles at 0.10–0.20 phr. The catalyst is metered as a 30–50% solution in dioctyl phthalate or another inert plasticiser to improve dispensing accuracy on PU foam machines. Microcellular PU elastomer (footwear midsoles, vibration mounts) uses T-9 at 0.05–0.15% on polyol weight as the gel catalyst.

Dental impression silicone (condensation-cure putty and light-body) uses T-9 at 0.30–0.50% — the lower toxicity profile compared to DBTDL is required for any product entering the oral cavity. Prosthetic and orthotic silicone (skin-contact body-forming RTV, scar treatment sheets) similarly specifies T-9 at 0.20–0.40%. Cosmetic skin-contact silicone (custom face moulds, special-effects make-up) uses T-9 at 0.30–0.60% in low-viscosity RTV formulations. Industrial RTV-1 for medical device assembly uses T-9 at 0.10–0.30% paired with alkoxysilane crosslinker — the longer cure time relative to DBTDL is acceptable in batch assembly where parts cure overnight.

Mandatory nitrogen blanket; CoA per shipment; 5 kg / 25 kg HDPE; 9-month shelf life sealed.

SEMITECH issues a CoA on every batch with: tin assay (ICP-OES, target 27.5–28.5%), active content (titration vs. iodine, target ≥95%), water content (Karl Fischer, target ≤0.2%), acid value (target 5–15 mg KOH/g), viscosity at 25°C, and APHA colour. Standard packing is 5 kg or 25 kg HDPE jerrycans, all sealed under dry nitrogen blanket. MOQ 5 kg for sample qualification, 25 kg for production. Lead time 1–2 weeks to Asia ports, 4–6 weeks to Europe and North America.

T-9 is the most air-sensitive of the tin catalysts — divalent Sn(II) oxidises to inactive Sn(IV) species on prolonged air exposure, forming brown-black precipitate. Mandatory: store sealed under nitrogen blanket below 25°C; re-blanket the headspace after each draw; consume opened drums within 30 days for consistent activity. Shelf life 9 months from manufacture date for sealed packaging (vs 12 months for the more stable Sn(IV) DBTDL/DOTL grades). REACH and regulatory: T-9 is REACH-registered for industrial PU and silicone catalyst use. Stannous (tin II) species are not subject to the dialkyltin(IV) Annex XVII restrictions, making T-9 the preferred organotin for skin- and food-contact applications. Toxicology dossier and SDS issued in EU/GHS format with every shipment.

T-9 is the divalent Sn(II) catalyst — the dominant gel catalyst in flexible PU foam (mattress, seating, automotive) and the lower-toxicity tin catalyst for dental, prosthetic, and skin-contact silicone applications. Mandatory nitrogen-blanket storage; oxidises to inactive Sn(IV) on air exposure. 9-month sealed shelf life. CoA per batch.

SEMITECH stocked grade; CoA per batch.