What Ethylene Glycol Grades Are Traded Internationally
Ethylene glycol (monoethylene glycol, MEG, CAS 107-21-1) is a bulk petrochemical intermediate made mainly by hydrating ethylene oxide. It is not one universal material. The market is split into grades defined by assay, by the content of diethylene glycol (DEG) and triethylene glycol (TEG), and by water content. DEG and TEG form in the same reaction as MEG, so the fractionation and finishing section of a plant decides which grades a producer can offer.
| Grade | Typical assay | Main outlet |
|---|---|---|
| Fibre / polyester grade | 99.9% min, DEG usually below 0.05% | PET resin, polyester fibre and film |
| Technical grade | 99.5% min | Unsaturated polyester resins, solvent blends |
| Coolant / industrial grade | 99.0% min | Antifreeze concentrates, de-icing fluids, heat transfer |
| DEG / TEG | Separate products | Polyester resins, gas dehydration, humectants |
Those figures describe ordinary commercial practice rather than a fixed law. The binding numbers are always the ones printed in the supplier specification and repeated in the certificate of analysis for the lot.
Fibre and Polyester Grade: The Dominant Outlet
Most global MEG consumption goes into polyester. In PET and polyester fibre plants the glycol is reacted with purified terephthalic acid, so reactive impurities in the MEG become part of the polymer chain. That is why fibre grade carries the tightest limits. Water is held low because moisture shifts the esterification balance, DEG is limited because it lowers the melting point of the finished polymer, and metal residues such as iron are controlled because they discolour the melt.
Buyers in this segment normally require a batch certificate showing assay, DEG, water, colour and iron, and they re-test incoming lots instead of relying on shipping documents alone.
Technical and Industrial Grades: Coolants, De-icing and Resins
Technical grade MEG does not need polymer-grade precision, because its customers do not build molecular chains around it. Its main outlets are:
Antifreeze and engine coolant concentrates, where MEG is blended with inhibitor packages and diluted on site to give freeze protection across a defined temperature range.
De-icing and anti-icing fluids, where the glycol is thickened and inhibited to meet a defined holdover performance.
Industrial heat transfer loops, where a water-glycol mixture carries heat between process units.
Unsaturated polyester resins, where MEG or a glycol blend supplies the diol component.
Solvent and processing aid duties in coatings, inks and printing, where the high boiling point keeps the formulation open long enough to level and flow.
Quality Control: Test Methods Written Into Contracts
Bulk glycol contracts usually name the method, not only the limit, so that buyer and seller test the same way. Methods that appear most often include ASTM D4052 for density, ASTM E203 for water by Karl Fischer titration, ASTM D1209 for colour on the platinum-cobalt scale, ASTM D1613 for acidity, and ASTM D445 for kinematic viscosity. Coolant performance is verified separately, for example ASTM D1177 for the freezing point of aqueous engine coolants and ASTM D1120 for their boiling point.
Storage, Packaging and Logistics Notes
Ethylene glycol is hygroscopic, so moisture pickup in storage is the main quality risk. Tanks are usually carbon steel or stainless steel and are kept under a dry gas blanket. Export parcels move as 200 kg or 230 kg drums, 1000 L intermediate bulk containers, road tankers or ISO tank containers. Because the material is harmful if swallowed and carries a specific target organ toxicity classification, shipments travel with a safety data sheet and hazard labels prepared in the applicable hazard communication format, and warehouse storage follows local rules for combustible and toxic liquids.
Frequently Asked Questions
Q: What is the difference between fibre grade and technical grade ethylene glycol?
A: Fibre grade is a higher-assay material with tighter limits on DEG, water and metal residues because it is polymerised into PET and polyester fibre. Technical grade is used where the glycol is blended or applied as a solvent rather than built into a polymer chain.
Q: Can technical grade MEG replace fibre grade in PET production?
A: It is not recommended. Elevated DEG and water shift the melt point and molecular weight of the polymer, so a substitution usually shows up as off-specification resin rather than as an immediate process failure.
Q: How is water content in ethylene glycol measured?
A: Karl Fischer titration to ASTM E203 is the standard approach. Glycol picks up atmospheric moisture quickly, so samples should be taken in closed containers and tested without delay.
Q: Is ethylene glycol the same as diethylene glycol?
A: No. Ethylene glycol is the two-carbon diol with CAS number 107-21-1. Diethylene glycol is a co-product with an extra ether linkage, a higher boiling point, and different uses and hazard labelling.
Q: What packaging is standard for export shipments?
A: 200 kg or 230 kg steel drums, 1000 L intermediate bulk containers and ISO tank containers are the common options. Nitrogen blanketing is often specified for tank and ISO container loads to hold water content within the agreed limit.
