Products›Silicone Materials›Curing Catalysts Hub›DOTL
DOTL (Dibutyltin Diacetate, CAS 1067-33-0): Long-Pot-Life Tin Catalyst for Cast-in-Place RTV and Large-Bead Extrusion
SEMITECH stocks DOTL at ≥98% purity — a moderate-activity organotin condensation catalyst that delivers tack-free times 30–50% longer than DBTDL at equivalent loading. Specified for cast-in-place sealants, hand-tooled large beads, and applications where extended working time matters more than absolute cure speed. 25 kg HDPE jerrycan, 2–4 week ex-China lead time.
Contents
| 1067-33-0 | ≥98% | 25 kg |
|---|---|---|
| CAS number | Active content | MOQ |
Chemistry & Specifications
Tetravalent tin(IV) bis-acetate; clear yellow liquid; MW 351.0; lower steric bulk than DBTDL with acetate byproduct.
DOTL (CAS 1067-33-0) is a tetravalent organotin with two n-butyl groups and two acetate ligands. MW 351.0 g/mol, density 1.31 g/cm³, Sn assay 33.0–34.0% by ICP-OES, active content ≥98%, water ≤0.1%, APHA ≤150. The acetate ligand paradoxically reduces Lewis acidity versus DBTDL's laurate, making DOTL approximately 30–50% slower at equivalent molar loading — the benefit is longer pot-life without risking under-cure in deep sections.
Cure Mechanism: Lower-Activity Sn(IV) Lewis Acid for Extended Working Time
Same fundamental chemistry as DBTDL — silanol activation and alkoxide condensation — at 30–50% lower rate.
DOTL catalyses silanol-alkoxysilane condensation via Lewis-acid coordination, giving tack-free times of 60–120 minutes at 23°C / 50% RH at 0.20% loading (vs 30–60 min for DBTDL).
- Loading 0.10–0.20% — long-pot-life RTV-1 sealants, vertical-bond overhead applications
- Loading 0.20–0.40% — standard cast-in-place RTV-2 mould rubber for prototype tooling
- Loading 0.40–0.80% — fast-cure DOTL formulations approaching DBTDL kinetics; rare in practice
DOTL is the catalyst of choice when the formulation requires extended hand-tooling time. Like DBTDL, DOTL poisons platinum addition-cure systems at ppm levels — segregate handling and metering.
▶Show full content (5 sections)
Applications & Formulation Guidance
Cast-in-place RTV moulds, hand-tooled architectural sealants, slow-cure RTV-2, alkyd transesterification.
RTV-2 condensation cast moulds — DOTL at 0.20–0.40% paired with TEOS or ethyl-silicate-40 gives a 45–90 minute pot-life and 24-hour cure. Hand-tooled architectural sealants use DOTL at 0.10–0.20% for 60–90 minute working time before skin formation. Alkyd resin transesterification at 200–230°C uses 0.05–0.15% on resin solids. Avoid DOTL on copper, brass, marble, or carbonate stone — acetate byproduct will stain or corrode; specify TBT or TET titanate for those substrates.
Procurement, Storage and Quality Control
CoA on every shipment, 25 kg HDPE under nitrogen blanket, 12-month shelf life sealed, 2–4 week ex-China.
SEMITECH issues a CoA on every batch: tin assay (ICP-OES, 33.0–34.0%), active content (≥98%), water (≤0.1%), APHA (≤150), density. Standard packing 25 kg HDPE jerrycans under nitrogen; 200 kg drums for bulk. MOQ 25 kg. Lead time 1–2 weeks to Asia, 4–6 weeks to Europe/North America. Re-blanket with nitrogen after each draw; consume opened drums within 45 days. DOTL (CAS 1067-33-0) is REACH-registered for industrial catalyst use.
DOTL Specification Sheet
SEMITECH stocked grade; CoA per batch.
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Dibutyltin diacetate | — |
| CAS number | 1067-33-0 | — |
| Molecular formula | C₁₂H₂₄O₄Sn | — |
| Molecular weight | 351.0 g/mol | — |
| Active content | ≥98% | Titration vs. KIO₃ |
| Tin (Sn) content | 33.0–34.0% | ICP-OES |
| Appearance | Clear pale-yellow to amber liquid | Visual |
| Density (20°C) | 1.30–1.32 g/cm³ | ASTM D1475 |
| Water content | ≤0.1% | Karl Fischer |
| APHA colour | ≤150 | ASTM D1209 |
| Flash point | >110°C (closed cup) | ASTM D93 |
| Solubility | Soluble in toluene, esters, ketones; insoluble in water | — |
| Packaging | 25 kg HDPE / 200 kg lined steel drum | — |
| Shelf life | 12 months sealed below 25°C | — |
FAQ
+When should I specify DOTL instead of DBTDL?
Specify DOTL when extended pot-life or hand-tooling window matters more than peak cure speed: cast-in-place RTV-2 mould making (45–90 min open time), large architectural sealant beads (60+ min), and slow-cure dental/prosthetic silicones. DOTL gives 30–50% longer tack-free times than DBTDL at the same loading.
+Will DOTL stain copper or marble substrates?
Possibly. The acetate byproduct is acetic acid, which corrodes copper/brass and etches marble and carbonate stones. For those substrates, specify TBT or TET titanate dealcoholisation-cure systems which release neutral alcohol byproduct.
+What pot-life can I expect from a DOTL-catalysed RTV-2 mould rubber?
A typical formulation (50,000 cP PDMS, ethyl-silicate-40 at 5–8%, DOTL at 0.30%, mineral filler 30%) gives 45–60 minute pot-life at 23°C. Lower DOTL to 0.20% for 60–90 min; raise to 0.50% for 25–35 min.