Thermoset comparison
Epoxy (DGEBA, amine-cured) vs Polyester (unsaturated, cast)
Every value below is a typical room-temperature figure with its source, test method and conditions — the same dataset that drives the calculators.
Which to choose
Epoxy bonds better, shrinks far less on cure and gives higher strength and toughness, which is why it dominates aerospace and high-performance composites. Unsaturated polyester is much cheaper and cures fast, at the cost of more cure shrinkage and styrene emissions. Polyester for boats, tanks and volume laminating; epoxy where performance and bond quality decide.
| Property | Epoxy (DGEBA, amine-cured) | Polyester (unsaturated, cast) | Difference |
|---|---|---|---|
| Density | 1.2 g/cm³ | 1.2 g/cm³ | identical |
| Young's modulus E | 3.45 GPa | 3.2 GPa | Epoxy (DGEBA, amine-cured) — 8% higher |
| Tensile strength | 70 MPa | 55 MPa | Epoxy (DGEBA, amine-cured) — 27% higher |
| Glass transition Tg | 120 °C | 75 °C | Epoxy (DGEBA, amine-cured) — 45 °C higher |
Where these numbers come from
- Daniel & Ishai, Engineering Mechanics of Composite Materials, 2nd ed.
- Callister & Rethwisch, Materials Science and Engineering, 10th ed.
Typical room-temperature values for learning and preliminary design; grades vary widely and a supplier datasheet always overrides a textbook figure. Confirm against the datasheet before design work.