4,4'-Methylenebiscyclohexylamine (PACM)
Key Features
- Near water-white color with exceptional UV stability for clear systems
- Long pot life (4-8 hrs) for large infusion and RTM applications
- High Tg potential (up to 140°C with post-cure) for structural composites
- Excellent through-cure in thick sections with extended working time
- Minimal color change on weathering — excellent outdoor durability
4,4'-Methylenebiscyclohexylamine (PACM), also known as bis(4-aminocyclohexyl)methane or hydrogenated MDA, is a cycloaliphatic diamine with outstanding UV stability, very low color contribution, and high glass transition temperature capability. PACM provides slow ambient-temperature cure with excellent through-cure depth and is widely used as a premium hardener for clear, water-white epoxy systems in UV-exposure environments. Its amine hydrogen equivalent weight (AHEW) is approximately 52.6 g/eq, requiring approximately 28 phr for standard BPA epoxy. PACM-cured systems exhibit Tg values of 120–140°C after proper post-cure (2 hours at 150°C), making it suitable for aerospace composites, tooling epoxies, and advanced structural laminates. The slow ambient reactivity (pot life 4–8 hours for 100g systems at 25°C) makes it suitable for large infusion layups, RTM systems, and thick-section laminates where extended working time is needed. PACM produces near-water-clear cured castings, making it the hardener of choice for optical and decorative clear epoxy applications. Often blended with faster-reacting hardeners to balance cure speed.
Specifications
| Parameter | Value |
|---|---|
| Appearance | Clear colorless liquid (low Tm grades) |
| Shelf Life | 24 months in sealed container |
| Density (25°C) | 0.950–0.953 g/cm³ |
| Viscosity (25°C) | 35–80 mPa·s |
| Pot Life (100g, 25°C) | 4–8 hours |
| Amine Hydrogen Equivalent Weight (AHEW) | ~52.6 g/eq |
Applications
FAQ
Pure PACM is a semi-crystalline solid with a melting point of approximately 35–55°C (varying by isomer ratio). Commercial grades are often offered as liquid blends with modified isomers or reactive diluents that remain liquid at room temperature. Always check the specific product form — solid PACM requires preheating before use, while liquid grades can be metered directly.
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