Aminosilane Sizing Agent for Carbon Fiber / Epoxy Interface
Key Features
- KH-550 (APTES) aminosilane dual-mechanism bonding — silanol to CF surface oxides + amine to epoxy matrix
- Restores 20–40% ILSS retention improvement in hot-wet conditioned CF/epoxy composites versus unsized fiber
- Compatible with bisphenol-A, multifunctional epoxy, and cyanate ester matrix systems for drone structures
- Simple water-based sizing bath application — 0.5–2.0 wt% aqueous solution at pH 4–5
- Low add-on level (0.5–2.0 wt% LOI) — minimal weight addition while maximizing interface chemistry
- Applied to CF fabrics and rovings before drone frame wet lay-up or prepreg manufacturing
A 3-aminopropyltriethoxysilane (APTES, KH-550) based sizing formulation designed for re-sizing desized carbon fiber rovings and fabrics used in drone frame composites. Commercial CF is supplied with a proprietary epoxy-compatible sizing from the fiber manufacturer; however, desized CF (required for thermoplastic matrix composites or after heat cleaning) or CF supplied without sizing must be re-treated before wet lay-up or prepreg manufacturing to restore the fiber-matrix interfacial adhesion that drives interlaminar shear strength (ILSS) and compression-after-impact (CAI) performance.
The aminosilane bridges the inorganic carbon fiber surface (surface oxidation groups: –COOH, –OH, –C=O) to the organic epoxy matrix through a dual chemical mechanism: silanol groups condense with surface oxides on the CF, while the terminal amine group reacts with epoxy groups in the matrix at cure temperature. This covalent cross-linking across the fiber-matrix interface prevents the moisture-induced interfacial debonding that degrades ILSS by 20–40% in untreated CF/epoxy composites after hot-wet conditioning.
Application is by aqueous sizing bath (0.5–2.0 wt% silane in water, pH 4–5) or dilute alcohol solution spray. After sizing, CF should be dried at 110–120°C for 30–60 minutes to complete silane condensation and remove residual solvent before lay-up. Compatible with standard bisphenol-A epoxy, multifunctional epoxy, and cyanate ester matrix systems.
Specifications
| Parameter | Value |
|---|---|
| CAS Number | 919-30-2 |
| Active ingredient | 3-Aminopropyltriethoxysilane (APTES, KH-550) |
| Purity (neat APTES) | ≥97.0% |
| Appearance (neat silane) | Colorless to pale yellow liquid |
| Flash point (neat APTES) | 96°C |
| Compatible matrix systems | Bisphenol-A epoxy, multifunctional epoxy, cyanate ester |
| Silane add-on level on fiber | 0.5–2.0 wt% LOI |
| Drying condition after sizing | 110–120°C, 30–60 min |
| ILSS improvement (CF/epoxy, hot-wet) | 20–40% retention improvement vs unsized CF |
| Recommended sizing bath concentration | 0.5–2.0 wt% in water (pH 4–5) |
Applications
FAQ
Prepare a 1.0–2.0 wt% silane solution: (1) Add water to a clean container (reverse addition prevents hydrolysis clumping); (2) Adjust pH to 4–5 with 1–2 drops of glacial acetic acid per liter of water; (3) While stirring, slowly add KH-550 at the target concentration; (4) Allow 30 minutes hydrolysis time at room temperature before use (solution will become slightly cloudy as silanols form); (5) Dip or pad the CF fabric through the bath, ensuring thorough wetting; (6) Squeeze to remove excess (target LOI 0.5–2.0 wt%); (7) Dry at 110–120°C for 30–60 minutes. Use the sizing bath within 8 hours of preparation — hydrolyzed silanol solutions are not stable for long storage.
Direct Contact
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