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 | — |
Industrial Application Scenarios
Chemistry & Coupling Mechanism
KR-38S is an isopropyl titanate carrying three N-ethylamino-ethylamino ligands (CAS 68442-54-6). The alkoxide portion anchors to hydroxyl sites on inorganic filler surfaces — silica, calcium carbonate, alumina, barium sulfate — via ligand exchange, forming stable Ti–O–M bonds. The pendant amine groups then react with epoxy groups in the matrix or coordinate with amine hardeners in polyurethane systems, creating a covalent organic–inorganic bridge. This dual reactivity distinguishes amino titanates from purely physical compatibilizers and explains their superior durability in amine-cure formulations. For mechanistic background, see the titanate coupling mechanism overview.
Performance in Epoxy and PU Systems
In mineral-filled epoxy adhesives, KR-38S improves lap-shear strength by 20–40% at 1–3 phr, attributable to reduced filler–resin interfacial voids and higher effective crosslink density near particle surfaces. Bond retention after 1,000 h at 85 °C/85% RH typically exceeds untreated controls by 15 percentage points — a critical metric for automotive and electronics adhesive qualifications. In two-component polyurethane systems, the secondary amine groups participate in urethane formation, directly contributing to crosslink density. Compared to KR-44 (longer alkyl chains for hydrophobicity), KR-38S prioritizes amine reactivity and is preferred wherever covalent integration with the cure chemistry is the design objective.
Compatibility & Processing
KR-38S is a yellow-to-amber liquid, fully miscible with isopropanol, MEK, toluene, and xylene, and stable ≥12 months sealed at room temperature. Optimal addition is filler pre-treatment at 0.5–2.0% by filler weight or in-situ resin addition at 1–3 phr. The titanate is stable to 200 °C and compatible with cure cycles from 80–160 °C. Hydrolytic sensitivity requires dry conditions during filler pre-treatment: moisture exposure before cure leads to premature Ti–O hydrolysis and loss of coupling efficiency. For water-based or high-humidity processing, KR-238S offers chelated ligands with substantially improved hydrolytic stability and is the recommended alternative.
Applications & Target Markets
KR-38S is specified in mineral-filled epoxy adhesives (electronics encapsulants, structural bonding), high-solids epoxy primers on steel and aluminum, filled polyurethane elastomers, and powder coatings with aluminum hydroxide or barium sulfate flame retardants. In coatings, 1–2 phr on 40–60 vol% filler loading recovers 3–5 gloss units lost to agglomeration and reduces mix viscosity by 15–25%, enabling higher filler targets without rheology penalty. Downstream demand is concentrated in automotive OEM adhesives, wind turbine blade composites, and consumer electronics underfill — segments growing at 6–9% CAGR driven by EV platform expansion and PCB miniaturization.
Frequently Asked Questions
Chemistry & Coupling Mechanism
KR-38S is an isopropyl titanate carrying three N-ethylamino-ethylamino ligands (CAS 68442-54-6). The alkoxide portion anchors to hydroxyl sites on inorganic filler surfaces — silica, calcium carbonate, alumina, barium sulfate — via ligand exchange, forming stable Ti–O–M bonds. The pendant amine groups then react with epoxy groups in the matrix or coordinate with amine hardeners in polyurethane systems, creating a covalent organic–inorganic bridge. This dual reactivity distinguishes amino titanates from purely physical compatibilizers and explains their superior durability in amine-cure formulations. For mechanistic background, see the titanate coupling mechanism overview.
Performance in Epoxy and PU Systems
In mineral-filled epoxy adhesives, KR-38S improves lap-shear strength by 20–40% at 1–3 phr, attributable to reduced filler–resin interfacial voids and higher effective crosslink density near particle surfaces. Bond retention after 1,000 h at 85 °C/85% RH typically exceeds untreated controls by 15 percentage points — a critical metric for automotive and electronics adhesive qualifications. In two-component polyurethane systems, the secondary amine groups participate in urethane formation, directly contributing to crosslink density. Compared to KR-44 (longer alkyl chains for hydrophobicity), KR-38S prioritizes amine reactivity and is preferred wherever covalent integration with the cure chemistry is the design objective.
Compatibility & Processing
KR-38S is a yellow-to-amber liquid, fully miscible with isopropanol, MEK, toluene, and xylene, and stable ≥12 months sealed at room temperature. Optimal addition is filler pre-treatment at 0.5–2.0% by filler weight or in-situ resin addition at 1–3 phr. The titanate is stable to 200 °C and compatible with cure cycles from 80–160 °C. Hydrolytic sensitivity requires dry conditions during filler pre-treatment: moisture exposure before cure leads to premature Ti–O hydrolysis and loss of coupling efficiency. For water-based or high-humidity processing, KR-238S offers chelated ligands with substantially improved hydrolytic stability and is the recommended alternative.
Applications & Target Markets
KR-38S is specified in mineral-filled epoxy adhesives (electronics encapsulants, structural bonding), high-solids epoxy primers on steel and aluminum, filled polyurethane elastomers, and powder coatings with aluminum hydroxide or barium sulfate flame retardants. In coatings, 1–2 phr on 40–60 vol% filler loading recovers 3–5 gloss units lost to agglomeration and reduces mix viscosity by 15–25%, enabling higher filler targets without rheology penalty. Downstream demand is concentrated in automotive OEM adhesives, wind turbine blade composites, and consumer electronics underfill — segments growing at 6–9% CAGR driven by EV platform expansion and PCB miniaturization.
+Q: What distinguishes KR-38S from silane coupling agents on non-siliceous fillers?
A: KR-38S outperforms silanes on non-siliceous fillers such as CaCO₃, BaSO₄, and Al(OH)₃ because titanates bond effectively across a filler pH range of 3–9, while silanes require surface silanols. On calcium carbonate at 50 vol% loading, KR-38S at 1.5 phr recovers approximately 90% of the viscosity reduction achievable with surface-treated grades, without the added cost of pre-treated filler supply.
+Q: What is the recommended loading level for KR-38S in epoxy adhesive formulations?
A: For in-situ addition, 1–3 phr relative to epoxy resin is the standard range. For filler pre-treatment, 0.5–2.0 wt% by filler weight is effective. Exceeding 3 phr rarely improves adhesion and can introduce plasticization, reducing cured Tg by 3–6 °C in highly filled systems — a meaningful loss in structural and elevated-temperature applications.
+Q: Is KR-38S compatible with common amine hardeners such as IPDA or DETA?
A: Yes, KR-38S is compatible with IPDA, DETA, and most cycloaliphatic and aliphatic amines. A pot-life reduction of 10–20% is possible in fast-cure systems because the secondary amine ligands participate in cure chemistry. Formulators should evaluate gel time on their specific hardener-resin-filler combination and adjust stoichiometry accordingly before committing to production scale.
+Q: How does moisture affect KR-38S during filler pre-treatment?
A: Moisture exposure before the coupling reaction is complete causes hydrolysis of the isopropoxide groups, generating isopropanol and forming insoluble titanium oxide oligomers. This sharply reduces coupling efficiency and can introduce haze or grit. Pre-treatment should be conducted in dry conditions (
+Q: When should KR-238S be chosen over KR-38S?
A: KR-238S uses neoalkoxy chelated ligands that resist hydrolysis, making it the correct choice for water-based systems, high-humidity compounding, or aqueous filler slurries. KR-38S provides stronger direct amine reactivity in dry solvent-based or melt-compounding processes. If the processing environment involves any free water contact before cure, KR-238S is the lower-risk selection.
+Q: What performance gains should buyers expect on aluminum substrates?
A: KR-38S bonds to the native Al₂O₃ passivation layer on aluminum via Ti–O–Al exchange, improving epoxy adhesive peel strength by 25–35% versus unprimed controls in standard lap-joint testing. Bond durability in salt-spray (500 h, 5% NaCl) also improves meaningfully, which is why KR-38S is specified in structural adhesive primers for automotive body-in-white and aerospace secondary structures.
+Ready to optimise your formulation?
Contact the Semitech technical team for product recommendations, samples and TDS.