# Monoethylene glycol: Characteristics

Why trace impurities turn polyester yellow

Source page: https://www.materialinsights.org/chemicals/meg/characteristics/

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.

Fibre-grade MEG must have very high purity and UV transmittance, because trace aldehydes and impurities discolour polyester. Coal-based MEG historically struggled to meet fibre-grade UV specs, which created a discount.

#### Properties that matter commercially

| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| **Purity** | fibre grade at least 99.9% MEG | Polyester colour and spinning stability. | industry standard (indicative) |
| **UV transmittance** | high at 220, 275 and 350 nm | Detects impurities that yellow polyester; coal MEG sometimes failed it. | industry standard (ASTM E2470, indicative) |
| **Freezing point (in water mix)** | 50:50 MEG/water freezes near -37°C | Antifreeze performance. | standard data |

#### Commercial grades

- Fibre grade (polyester, PET)
- Industrial or antifreeze grade
- Bio-MEG (partially bio-based PET)

## Other sections

- [Summary](https://www.materialinsights.org/chemicals/meg/index.md)
- [Overview](https://www.materialinsights.org/chemicals/meg/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/meg/correlation/index.md)
- [Production route](https://www.materialinsights.org/chemicals/meg/routes/index.md)
- [Production](https://www.materialinsights.org/chemicals/meg/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/meg/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/meg/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/meg/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/meg/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/meg/regulation/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/meg/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/meg/links/index.md)