Cycloaliphatic Epoxy Resin (EEW 125-145)
Key Features
- UV-cationic curable without oxygen inhibition
- Outstanding UV/weathering resistance — no yellowing
- Superior arc and tracking resistance for outdoor electrical
- High purity for optical and semiconductor applications
- Excellent electrical insulation (dielectric strength >20 kV/mm)
Cycloaliphatic Epoxy Resin (EEW 125-145 g/eq, CAS 2386-87-0) is 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, the benchmark cycloaliphatic diepoxide for UV-cationic curing and high-performance electrical applications. The oxirane groups are directly incorporated into alicyclic rings, conferring exceptional UV/weathering resistance, arc resistance, and tracking resistance unachievable with glycidyl ether-based epoxies.
Cycloaliphatic epoxy cures by cationic photoinitiators (diaryliodonium or triarylsulfonium salts) under UV irradiation without the oxygen inhibition problem of radical-cure acrylates, enabling use in UV-curable coatings, UV-curable adhesives, and UV LED curing systems for electronics. In thermally cured systems with anhydrides (MTHPA, HHPA) and Lewis acid catalysts, it provides Tg values of 150-175°C with outstanding electrical insulation (dielectric strength >20 kV/mm, dissipation factor <0.003 at 1 MHz).
Principal applications include outdoor electrical insulator encapsulation (arc-resistant, tracking-resistant), UV-cured electronics conformal coatings, cycloaliphatic epoxy/anhydride cast electrical insulators (medium-voltage bushings, switchgear), and high-purity optical epoxy systems where aromatic epoxies would cause yellowing. Unlike glycidyl ether epoxies, cycloaliphatic epoxy shows negligible yellowing under UV exposure, making it the preferred choice for long-life outdoor electrical applications.
Specifications
| Parameter | Value |
|---|---|
| Appearance | Water-white to slightly yellow liquid |
| Color (APHA) | ≤50 |
| Density (25°C) | 1.17-1.18 g/cm³ |
| Tg (MTHPA cured) | 150-175°C |
| Viscosity (25°C) | 350-500 mPa·s |
| Dielectric Strength | >20 kV/mm |
| Epoxy Equivalent Weight | 125-145 g/eq |
Applications
FAQ
Diaryliodonium salts (e.g., diphenyliodonium hexafluoroantimonate, 1-3 phr) and triarylsulfonium hexafluorophosphate salts (1-3 phr) are the standard UV-cationic photoinitiators. Diaryliodonium salts are more reactive but may cause slight yellowing at high loading; triarylsulfonium salts provide better thermal stability. UV LED curing (365-395 nm) requires photoinitiators with absorption in that range — some commercial grades are specifically optimized for 365 nm LED sources. Sensitizers (anthracene, isopropylthioxanthone) can extend the absorption window for LED curing systems.
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