Hardeners
Paint chemicals 2025-03-21
1. Performance Features
Hardeners are prepared using high-quality polyisocyanates. They have a high solid content and
excellent leveling, drying, weather resistance, and hardness.
2. Applications
Use in combination with two-component basecoat or clearcoat
Hardeners: Technical Overview
Hardeners (curing agents) are essential components in thermosetting polymer systems, enabling crosslinking to achieve final material properties. Below is a structured technical summary:
1. Key Hardener Types & Properties
| Type | Chemical Basis | Cure Temp | Pot Life | Key Features |
|---|---|---|---|---|
| Amines | Aliphatic/Aromatic amines | RT-150°C | 10min-24hr | Fast cure, high reactivity |
| Polyamides | Polyamine derivatives | RT-100°C | 1-8hr | Flexible, good adhesion |
| Anhydrides | Acid anhydrides | 80-200°C | 1-4hr | High Tg, low exotherm |
| Isocyanates | -NCO functional groups | RT-120°C | 5min-2hr | Moisture-sensitive, tough films |
| Catalytic | Lewis acids/bases | 50-250°C | N/A | Latent, heat-activated |
2. Performance Comparison
| Parameter | Amines | Polyamides | Anhydrides | Isocyanates |
|---|---|---|---|---|
| Cure Speed | Very Fast | Moderate | Slow | Fast |
| Flexibility | Low | High | Medium | High |
| Chemical Resistance | Excellent | Good | Excellent | Good |
| Moisture Tolerance | Poor | Good | Excellent | Poor |
3. Application Guidelines
| Resin System | Recommended Hardener | Mix Ratio | Cure Schedule |
|---|---|---|---|
| Epoxy | Amines/Polyamides | 1:1 to 1:4 | RT-24hr or 80°C-2hr |
| Polyester | Peroxides (MEKP) | 1-3% | RT-6hr or 60°C-1hr |
| Polyurethane | Isocyanates | 1:1 to 1:1.1 | RT-48hr or 80°C-30min |
| Phenolic | Hexamethylenetetramine | 5-15% | 150°C-30min |
4. Selection Criteria
| Factor | Considerations |
|---|---|
| Substrate | Metals: Amines/Anhydrides; Plastics: Polyamides |
| Service Temp | >150°C: Anhydrides; <80°C: Polyamides |
| Pot Life | Short: Amines; Long: Polyamides/Anhydrides |
| Regulatory | Low-VOC: Catalytic; Food-contact: Anhydrides |
5. Limitations & Solutions
| Issue | Mitigation |
|---|---|
| Skin Irritation (Amines) | Use PPE; substitute with modified amines |
| Moisture Sensitivity | Pre-dry substrates; use anhydrides |
| High Exotherm | Reduce cure rate; use latent hardeners |
Conclusion
Hardeners critically define cure kinetics and end-use properties of thermosets. Selection depends on resin chemistry, processing conditions, and performance requirements.
