The aminoethylaminopropyl-terminated polydimethylsiloxane (AEAPS, diamino-terminated silicone oil) is highly suitable for polyurethane stain-resistant modification. It can significantly improve the hydrophobicity, low surface energy and stain resistance of coatings. Below are the core parameters and application points:
1. Core Conclusion and Applicability Basis
✅ Applicable: The amino groups at both ends of AEAPS react with the NCO groups of polyurethane to form urea bonds, introducing siloxane segments into the polyurethane main chain. This endows the material with low surface energy, weather resistance, stain resistance, while improving mechanical and heat resistance properties.
✅ Stain-resistant Mechanism: The siloxane segments migrate to the surface, forming a dense hydrophobic layer, reducing the surface tension (about 20-22 mN/m), which makes stains difficult to adhere and easy to clean.
2. Selection of Key Parameters
2.1 Dosage Range
| Application Scenario | Recommended Dosage (mass fraction) | Performance Characteristics |
|---|---|---|
| Solvent-based polyurethane elastomer | 3%-15%, optimal at 10% | Optimal balance between comprehensive mechanical properties and stain resistance; contact angle is significantly improved |
| Water-based polyurethane (waterproof/stain-resistant) | 5%-20%, up to 20% maximum | Waterproof rating reaches 90+; surface energy is obviously reduced |
| Polyurethane coating/adhesive | 2%-8% | Balances adhesion and stain resistance; avoids compatibility issues caused by excessive dosage |
2.2 Viscosity (25℃) and Molecular Weight Matching
| Viscosity Range | Corresponding Molecular Weight | Application Scenario | Advantages |
|---|---|---|---|
| 100-500 mPa·s (low viscosity) | 1000-3000 | Water-based polyurethane, high-speed dispersion system | Easy to disperse, fast reaction with NCO, good compatibility |
| 500-5000 mPa·s (medium viscosity) | 3000-10000 | Solvent-based polyurethane, elastomer | Balances dispersibility and siloxane mobility |
| 5000-50000 mPa·s (high viscosity) | 10000-50000 | Thick coating, high-performance elastomer | High siloxane content, better stain resistance and durability |
2.3 Amine Value (mmol/g) Selection
| Amine Value Range | Reaction Activity | Application Scenario | Notes |
|---|---|---|---|
| 0.2-0.4 | Medium | Occasions with high requirements for weather resistance and anti-yellowing | Low yellowing risk, suitable for light-colored coatings |
| 0.4-0.6 | High | General-purpose polyurethane modification | Balances reactivity and stability; excellent stain-resistant effect |
| 0.6-1.0 | Very high | Fast-curing systems, high requirements for crosslinking density | Pay attention to the yellowing caused by amino oxidation; it is recommended to add antioxidants |
Core Principle: The amine value determines the crosslinking density and reaction rate, which needs to be matched with the NCO/OH ratio to avoid gelation or insufficient curing.
3. Application Advantages and Precautions
3.1 Advantages
- Diamino Activity: The primary amino groups at both ends have high reactivity with NCO (about 120 kJ/mol), forming stable urea bonds and improving interfacial adhesion.
- Controllable Structure: The terminated structure ensures uniform distribution of siloxane segments and high migration efficiency, leading to long-lasting stain resistance.
- Performance Synergy: It simultaneously improves stain resistance, weather resistance, high/low temperature resistance and mechanical properties, which is superior to monoamino-modified alternatives.
3.2 Precautions
- Compatibility Control: It is recommended to pre-dilute high-viscosity/high-amine-value products (e.g., use ethyl acetate for solvent-based systems, co-solvents for water-based systems) to avoid agglomeration.
- Yellowing Risk: Amino groups are prone to oxidation. For light-colored systems, it is preferable to select products with low amine value (< 0.3 mmol/g) or add antioxidants (e.g., BHT).
- Reaction Conditions: The reaction should be carried out under N₂ protection, and the temperature should be controlled at 60-80℃ to avoid amino decomposition at high temperatures.
4. Summary
AEAPS is the preferred material for polyurethane stain-resistant modification. It is recommended to select the combination according to the following criteria:
- General-purpose type: dosage 5%-10%, viscosity 500-2000 mPa·s, amine value 0.4-0.6 mmol/g
- Water-based system: dosage 10%-15%, viscosity 100-500 mPa·s, amine value 0.3-0.5 mmol/g
- High-performance elastomer: dosage 8%-12%, viscosity 2000-5000 mPa·s, amine value 0.5-0.8 mmol/g
-
Links