Silicone Curing Catalysts: SEMITECH Portfolio — Tin, Platinum, Peroxide & Titanate Catalysts for RTV / HTV / LSR Systems
SEMITECH supplies 8 silicone curing catalyst grades covering condensation, addition, peroxide, and titanate-chelate cure chemistries — Karstedt platinum, DBTDL tin, DCBP peroxide and chelated titanates manufactured under ISO-9001 with 2–4 week ex-China lead times.
Contents
| 8 | 2–4 wk | 25 kg |
|---|---|---|
| Catalyst grades in portfolio | Ex-China lead time | MOQ (most grades) |
Silicone Curing Mechanisms: Why Catalyst Choice Defines Your Process
Three fundamentally different chemistries — condensation, addition, peroxide — each requiring its own catalyst class. Mismatching produces silent process failures.
Condensation cure (RTV-1, RTV-2, dental impression) crosslinks silanol-terminated PDMS with tetra-functional silanes, requiring a tin or titanate catalyst. Addition cure (LSR, RTV-2 medical, optical) joins vinyl-PDMS to Si-H crosslinkers via hydrosilylation with a platinum complex — no byproduct released. Peroxide cure (HTV, extruded profiles, cable jackets) generates free radicals at 120–170°C. Mismatching catalyst to chemistry produces silent failures, and platinum is catastrophically poisoned by sulphur, amines, organotin, and phosphorus species at ppm levels.
Tin Catalysts (DBTDL / DOTL / T-9): Condensation Cure Workhorses
Organotin grades (DBTDL, DOTL, T-9 stannous octoate) — the dominant condensation-cure class for RTV silicones, polyurethane elastomers, and ester transesterification.
- DBTDL (CAS 77-58-7) — highest-activity tin catalyst; 0.05–0.5% in RTV silicone, 0.01–0.1% in PU systems
- DOTL (CAS 1067-33-0) — 30–50% slower than DBTDL; longer working time for cast-in-place sealants
- T-9 (CAS 301-10-0) — divalent Sn(II), preferred where DBTDL toxicity flagged in EU REACH downstream-use scenarios
All three hydrolyse on prolonged moisture exposure. Store sealed under nitrogen; consume opened drums within 60 days.
▶Show full content (6 sections)
Platinum Catalysts (Karstedt / Speier): Addition Cure for LSR & RTV-2
Karstedt and Speier platinum complexes for hydrosilylation in LSR injection moulding, RTV-2 medical and optical, and food-contact silicones.
Karstedt (Pt-DVTMDS complex, 2/3/5% Pt in vinyl-siloxane) is the modern standard — far more active and selective than Speier, no chloride residue, no discolouration. Typical use level 5–20 ppm Pt. Speier (H₂PtCl₆·6H₂O, CAS 18497-13-7) is the lower-cost alternative accepted where chloride residue and cure colour are tolerable.
Peroxide & Titanate Catalysts (DCBP / TBT / TET): Specialty Roles
DCBP for HTV cable jackets and HCR profiles; TBT / TET for dealcoholisation-cure RTV on sensitive substrates (mirror glass, copper, marble).
DCBP (CAS 133-14-2) — lowest-decomposition-temperature peroxide for HTV silicone, supplied as 50% paste in silicone fluid. TBT (CAS 5593-70-4) and TET (titanium acetylacetonate, Tyzor AA-equivalent) function as condensation-cure catalysts releasing neutral alcohol byproduct — specified for copper, marble, and mirror-grade glass where acetic-acid byproduct from tin-cure would corrode.
Procurement, Storage and Quality Control
CoA on every shipment, batch-level active-component assay, MOQ 25 kg for tin/titanate grades, 1 kg for Karstedt 5%.
SEMITECH issues CoA with active-component assay (Pt by ICP-MS, Sn by XRF, peroxide by iodometric titration), water content, and colour. MOQ 25 kg for tin/titanate, 1 kg for Karstedt. Lead time 2–4 weeks to SE Asia, 4–6 weeks to Europe/North America. Storage discipline critical: tin catalysts hydrolyse, platinum is poisoned by sulphur/amine vapours, peroxides decompose at elevated temperature. Store sealed, below 25°C, in original packaging.
SEMITECH Catalyst Grade Reference: Key Specifications
Eight stocked grades with chemistry, CAS, cure type, active content, typical loading, and primary application.
| Grade | Chemistry / CAS | Cure Type | Active Content | Typical Loading | Primary Application |
|---|---|---|---|---|---|
| DBTDL | Dibutyltin dilaurate / 77-58-7 | Condensation | ≥97% (Sn 18.0–18.5%) | 0.05–0.5% | RTV-1/RTV-2 silicone, PU |
| DOTL | Dibutyltin diacetate / 1067-33-0 | Condensation | ≥98% | 0.1–0.8% | Long-pot-life RTV sealants |
| T-9 | Stannous octoate / 301-10-0 | Condensation / PU | ≥95% (Sn 28%) | 0.05–0.3% | PU foam, dental silicone |
| Karstedt 5% | Pt-divinyl-tetramethyldisiloxane complex | Addition | 5.0% Pt in vinyl-siloxane | 5–20 ppm Pt | LSR, RTV-2, optical encapsulation |
| Speier (H₂PtCl₆) | Chloroplatinic acid·6H₂O / 18497-13-7 | Addition / hydrosilylation | ≥99% (in IPA solution) | 10–50 ppm Pt | Industrial RTV-2, silane synthesis |
| DCBP 50% paste | Bis(2,4-dichlorobenzoyl) peroxide / 133-14-2 | Peroxide (free radical) | 50% in silicone fluid | 0.5–1.5 phr | HTV silicone, hot-air vulcanisation |
| TBT | Tetra-n-butyl titanate / 5593-70-4 | Condensation (titanate) | ≥98% (TiO₂ 14.0–14.3%) | 0.5–2.0% | Dealcoholisation-cure RTV, PET catalyst |
| TET (Ti AcAc) | Titanium acetylacetonate (Tyzor AA-eq.) | Condensation (chelated) | 75% in IPA | 0.5–2.0% | Waterborne coatings, 1K RTV |
FAQ
+Which catalyst should I use for two-part LSR injection moulding?
Karstedt platinum complex at 2–5% Pt loading. Dose 5–20 ppm Pt in the A-side; cure cycle 10–30 seconds at 150–200°C. Preferred over Speier because no chloride byproducts.
+Why does my platinum-cured silicone fail to cure on certain substrates?
Platinum is poisoned by sulphur, tertiary amines, organotin, phosphorus species, and lead/mercury. Solutions: switch to sulphur-free elastomer moulds; pre-bake substrates; use a barrier primer; or increase Pt dosage to 30–50 ppm.
+DBTDL or DOTL for RTV-1 sealants?
DBTDL gives 30–60 min tack-free at 0.1% loading; DOTL gives 60–120 min. Specify DBTDL for fast skin formation; DOTL for longer working windows. Choice is handling, not final properties.
+Is DBTDL still allowed under EU REACH?
DBTDL (CAS 77-58-7) remains permitted as an industrial curing catalyst. The Annex XVII restrictions target skin-contact and food-contact articles. For consumer-facing applications, specify T-9 or switch to addition-cure platinum.
+What is the MOQ and lead time for Karstedt?
MOQ 1 kg for 2/3% Pt grades, 500 g for 5% Pt. Lead time 2–3 weeks to Asia, 3–4 weeks to Europe/North America. Samples (50–100 g) ship within 5 working days.
+Can I switch from tin-catalysed to titanate-catalysed RTV without reformulating?
Direct substitution is not recommended. Reformulation involves switching crosslinker to alkoxy-functional silane, raising titanate dosage to 1–2%, and qualifying 2–3x slower cure rate. Titanate-cure is the right choice for copper, marble, or mirror substrates.
Related SEMITECH Product Hubs
Other portfolios from the SEMITECH catalog that complement this hub — adjacent product families and cross-application materials.