Technical Specifications
| Parameter | Value | Test Method |
|---|---|---|
| Chemical name | Di(dioctyl pyrophosphato) Oxoethylene Titanate | — |
| CAS number | 65460-52-8 | — |
| Appearance | Light yellow to amber liquid | Visual |
| Active content | ≥95% | GC |
| Density (25°C) | 0.96–1.00 g/cm³ | ASTM D792 |
| Viscosity (25°C) | 80–200 mPa·s | ASTM D7042 |
| Flash point (PMCC) | >110°C | ASTM D93 |
| Titanium content | ~7.5 wt% | ICP-OES |
| Recommended dosage | 0.5–2.0% on filler weight | — |
| Max processing temp. | 220°C continuous / 250°C short-term | — |
| Shelf life | 24 months (sealed, below 30°C) | — |
Industrial Application Scenarios
Coordinate-Type Mechanism: Why It Outperforms Single-Alkoxy Grades
KR-26S achieves surface coupling through a coordinate bonding pathway rather than the hydrolysis-driven mechanism of single-alkoxy titanates. The oxoethylene (ethylene glycol) bridging group forms a chelate-like coordination with Lewis-acid sites on mineral surfaces — calcium carbonate, talc, barium sulfate — without consuming surface hydroxyl groups. This makes KR-26S effective on low-hydroxyl fillers where monoalkoxy grades such as KR-9S underperform. The two dioctyl pyrophosphato organofunctional groups orient toward the polymer matrix, generating a hydrophobic interphase that reduces melt viscosity and suppresses filler agglomeration. For detailed mechanism background, see the titanate coupling mechanism reference page.
Performance in High-Filler-Loading Thermoplastic Systems
High-filler thermoplastic compounds — those carrying mineral loads above 50 wt% — generate extreme interfacial area that exhausts standard coupling agents and causes viscosity spikes, poor dispersion, and mechanical property collapse. KR-26S stabilizes these systems by forming a monolayer on each filler particle, physically separating particles and lubricating the polymer–filler interface. Laboratory data for 70 wt% CaCO₃-filled polypropylene show a 35–45% reduction in melt flow index drift versus untreated controls, with tensile elongation at break improving from below 15% to above 40%. For moisture-sensitive applications, compare with KR-138S.
Processing Conditions and Dosage Protocol
KR-26S is a light amber liquid at room temperature, miscible with aliphatic and aromatic hydrocarbon diluents but incompatible with protic solvents. Pre-coating the filler before compounding delivers the best results: dilute KR-26S to 10–20% in mineral spirits, spray onto filler, then dry at 80°C for 30 minutes before introduction to the twin-screw extruder. Masterbatch addition at the throat is the alternative for continuous lines. Dosage is 0.5–1.5% on filler weight for carbonate fillers; increase to 1.5–2.0% for high-surface-area silicates (BET > 10 m²/g). Do not exceed 250°C barrel temperature — above this threshold the pyrophosphato groups begin to dissociate.
Polymer Compatibility and Target Application Matrix
KR-26S is formulated for non-polar and moderately polar thermoplastics: polypropylene, polyethylene, EVA, TPE, and nylon 6 at filler loadings up to 40 wt%. It performs poorly in highly polar matrices such as PVC or polyester without compatibilizer addition. Primary end-use segments include automotive interior components (PP/talc), halogen-free flame-retardant cable jacketing (PE/CaCO₃ at 60–70 wt%), and rubber goods with whitened mineral fillers. For reactive compounding lines or systems requiring maximum hydrolysis resistance, evaluate KR-9S as the monoalkoxy alternative.
Frequently Asked Questions
Coordinate-Type Mechanism: Why It Outperforms Single-Alkoxy Grades
KR-26S achieves surface coupling through a coordinate bonding pathway rather than the hydrolysis-driven mechanism of single-alkoxy titanates. The oxoethylene (ethylene glycol) bridging group forms a chelate-like coordination with Lewis-acid sites on mineral surfaces — calcium carbonate, talc, barium sulfate — without consuming surface hydroxyl groups. This makes KR-26S effective on low-hydroxyl fillers where monoalkoxy grades such as KR-9S underperform. The two dioctyl pyrophosphato organofunctional groups orient toward the polymer matrix, generating a hydrophobic interphase that reduces melt viscosity and suppresses filler agglomeration. For detailed mechanism background, see the titanate coupling mechanism reference page.
Performance in High-Filler-Loading Thermoplastic Systems
High-filler thermoplastic compounds — those carrying mineral loads above 50 wt% — generate extreme interfacial area that exhausts standard coupling agents and causes viscosity spikes, poor dispersion, and mechanical property collapse. KR-26S stabilizes these systems by forming a monolayer on each filler particle, physically separating particles and lubricating the polymer–filler interface. Laboratory data for 70 wt% CaCO₃-filled polypropylene show a 35–45% reduction in melt flow index drift versus untreated controls, with tensile elongation at break improving from below 15% to above 40%. For moisture-sensitive applications, compare with KR-138S.
Processing Conditions and Dosage Protocol
KR-26S is a light amber liquid at room temperature, miscible with aliphatic and aromatic hydrocarbon diluents but incompatible with protic solvents. Pre-coating the filler before compounding delivers the best results: dilute KR-26S to 10–20% in mineral spirits, spray onto filler, then dry at 80°C for 30 minutes before introduction to the twin-screw extruder. Masterbatch addition at the throat is the alternative for continuous lines. Dosage is 0.5–1.5% on filler weight for carbonate fillers; increase to 1.5–2.0% for high-surface-area silicates (BET > 10 m²/g). Do not exceed 250°C barrel temperature — above this threshold the pyrophosphato groups begin to dissociate.
Polymer Compatibility and Target Application Matrix
KR-26S is formulated for non-polar and moderately polar thermoplastics: polypropylene, polyethylene, EVA, TPE, and nylon 6 at filler loadings up to 40 wt%. It performs poorly in highly polar matrices such as PVC or polyester without compatibilizer addition. Primary end-use segments include automotive interior components (PP/talc), halogen-free flame-retardant cable jacketing (PE/CaCO₃ at 60–70 wt%), and rubber goods with whitened mineral fillers. For reactive compounding lines or systems requiring maximum hydrolysis resistance, evaluate KR-9S as the monoalkoxy alternative.
+Q: What makes KR-26S different from single-alkoxy titanate coupling agents like KR-9S?
A: KR-26S bonds to filler surfaces through coordinate chemistry rather than hydrolytic alkoxy displacement, making it effective on low-hydroxyl fillers such as CaCO₃ and BaSO₄ where single-alkoxy grades like KR-9S show limited activity. This mechanism difference accounts for KR-26S’s superior performance at filler loadings above 50 wt%, where hydroxyl site exhaustion renders monoalkoxy types ineffective.
+Q: What filler loading levels can KR-26S support in polypropylene compounds?
A: KR-26S can stabilize polypropylene systems carrying up to 70–75 wt% calcium carbonate while maintaining processable melt viscosity and elongation at break above 30%. Without coupling treatment, compounds above 55 wt% typically exhibit melt fracture and brittle failure. Dosage should be increased proportionally with filler surface area as loading rises above 60 wt%.
+Q: What is the recommended dosage of KR-26S on different filler types?
A: For coarse calcium carbonate (d50 > 5 µm, BET
+Q: Is KR-26S thermally stable enough for engineering thermoplastic processing temperatures?
A: KR-26S is rated for continuous processing up to 220°C and tolerates short-term excursions to 250°C, covering most PP and PE compounding lines. Above 250°C the dioctyl pyrophosphato groups begin dissociating, which can release phosphoric acid species and degrade coupling efficiency. For nylon 6 or ABS systems processed above 230°C, evaluate the higher-stability KR-138S instead.
+Q: Can KR-26S be used in halogen-free flame-retardant cable compounds?
A: Yes. KR-26S is widely used in HFFR cable jacketing compounds based on PE and EVA matrices with 60–70 wt% ATH or magnesium hydroxide filler. The pyrophosphato functionality is compatible with hydroxide filler surfaces, improves particle dispersion, reduces compound viscosity, and contributes marginally to char formation. Confirm compatibility with specific FR system formulations before production scale-up.
+Q: How should KR-26S be stored and handled safely?
A: Store sealed in original containers below 30°C, away from moisture and strong acids. Shelf life is 24 months from manufacture date under correct storage conditions. KR-26S is not classified as hazardous under GHS at normal handling concentrations, but use nitrile gloves and eye protection. Flash point exceeds 110°C, so standard storage practices — no open flames, good ventilation — are sufficient.
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