Monoethylene glycol: Characteristics
Why trace impurities turn polyester yellow
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)