Epoxy resins: Characteristics
Epoxy equivalent weight and what it tells you
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Buyers specify epoxy by epoxy equivalent weight (EEW), viscosity, colour and hydrolysable chlorine. These set the hardener ratio, processing time and the electrical and corrosion performance of the cured product.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Epoxy equivalent weight | LER about 180-195 g/eq; solid resins about 450-2,000 g/eq (indicative) | Sets hardener dose and crosslink density | indicative, producer data sheets |
| Viscosity at 25 C | LER about 11,000-14,000 mPa s (indicative) | Processing and infusion in blades | indicative |
| Hydrolysable chlorine | below about 500 ppm; electronic grades much lower (indicative) | Chloride corrodes circuits | indicative |
| Glass transition after cure | about 120-180 C depending on hardener (indicative) | Heat resistance of laminates and composites | indicative |
Commercial grades
- Standard LER (coatings, composites)
- Solid epoxy resins (powder coatings)
- Brominated epoxy (FR-4 laminates)
- Novolac epoxy (high temperature, electronics)
- Bisphenol F (low viscosity)
- Wind-blade infusion systems