SEMITECH KR-38S — Isopropyl Tri(N-ethylamino-ethylamino) Titanate
Technical Specifications
| Parameter | Value | Test Method |
|---|---|---|
| CAS Number | 68442-54-6 | — |
| Chemical Name | Isopropyl tri(N-ethylamino-ethylamino) titanate | — |
| Appearance | Yellow to amber liquid | Visual |
| Active Content | ≥95% | GC |
| Titanium Content | 11.0–12.0% | ICP-OES |
| Viscosity (25 °C) | 50–150 mPa·s | ASTM D445 |
| Flash Point | >60 °C (closed cup) | ASTM D93 |
| Thermal Stability | Stable to 200 °C | TGA |
| Recommended Loading (in-situ) | 1–3 phr (epoxy resin basis) | — |
| Recommended Loading (pre-treat) | 0.5–2.0 wt% on filler | — |
| Shelf Life | 12 months, sealed, ≤30 °C | — |
| Packaging | 20 kg / 200 kg drums | — |
Chemistry & Coupling Mechanism
KR-38S carries three N-ethylamino-ethylamino ligands. The alkoxide anchors to filler surfaces (silica, CaCO₃, alumina, BaSO₄) via ligand exchange, while the pendant amine groups react with epoxy groups or coordinate with amine hardeners in PU systems — creating a covalent organic-inorganic bridge. This dual reactivity distinguishes it from purely physical compatibilizers.
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Performance in Epoxy and PU Systems
In mineral-filled epoxy adhesives, KR-38S improves lap-shear strength 20–40% at 1–3 phr. Bond retention after 1,000 h at 85°C/85% RH exceeds untreated controls by 15 percentage points. In two-component PU, secondary amines participate directly in urethane formation. Compared to KR-44, KR-38S prioritizes amine reactivity over hydrophobicity.
Compatibility & Processing
Miscible with IPA, MEK, toluene, and xylene. Stable to 200°C, compatible with 80–160°C cure cycles. Hydrolytic sensitivity requires dry conditions during filler pre-treatment. For water-based or high-humidity processing, KR-238S with chelated ligands is the recommended alternative.
Applications
Mineral-filled epoxy adhesives, high-solids epoxy primers, filled PU elastomers, and powder coatings with ATH or BaSO₄ flame retardants. In coatings, 1–2 phr recovers 3–5 gloss units lost to agglomeration and reduces viscosity 15–25%.
Frequently Asked Questions
+Q: What distinguishes KR-38S from silane coupling agents on non-siliceous fillers?
A: KR-38S bonds effectively across filler pH 3–9, while silanes require surface silanols. On CaCO₃ at 50 vol%, KR-38S at 1.5 phr recovers ~90% of the viscosity reduction achievable with pre-treated filler grades.
+Q: What is the recommended loading for epoxy adhesives?
A: In-situ: 1–3 phr on epoxy resin. Filler pre-treatment: 0.5–2.0 wt% on filler weight. Above 3 phr can reduce cured Tg by 3–6°C in highly filled systems.
+Q: Is KR-38S compatible with amine hardeners?
A: Yes — compatible with IPDA, DETA, and most cycloaliphatic amines. Pot-life reduction of 10–20% is possible; evaluate gel time before production.
+Q: When should KR-238S be chosen over KR-38S?
A: KR-238S resists hydrolysis and is correct for water-based systems, high-humidity compounding, or aqueous filler slurries. KR-38S provides stronger amine reactivity in dry solvent-based or melt-compounding processes.
+Q: What performance gains on aluminum substrates?
A: Epoxy adhesive peel strength improves 25–35% versus unprimed controls via Ti–O–Al exchange with the native Al₂O₃ layer. Salt-spray durability (500 h) also improves significantly.
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