Polyethylene glycol (PEG) is one chemical family sold in many grades. The number after "PEG" is the average molecular weight. That single number decides whether the product is a thin liquid, a paste or a waxy solid, and therefore what it is used for.
Liquid, soft or solid
| Grade | Form at room temperature | Typical uses |
|---|---|---|
| PEG 200 | Clear, thin liquid | Solvent and humectant, plasticiser for paper and glues, chemical intermediate |
| PEG 400 | Clear liquid | Pharma solvent for soft-gel and oral liquids, cosmetics humectant, textile and lubricant formulations |
| PEG 600 | Clear liquid; may haze when cold | Cosmetic creams, metalworking fluids, rubber processing |
| PEG 1500 | Soft waxy solid | Ointment bases, suppository blends |
| PEG 4000 | White waxy flakes or powder | Tablet binder and lubricant, ceramics binder, paper and textile auxiliaries |
| PEG 6000 | White flakes or powder, higher melting | Tablet coating and binder, lubricant for rubber moulding, ceramics |
The spec that proves the grade: hydroxyl value
Each PEG molecule has two hydroxyl (–OH) end groups, so the hydroxyl value falls as the molecules get longer. A handy check is: average molecular weight ≈ 112,200 ÷ hydroxyl value. For PEG 400, expect a hydroxyl value of about 265–295 mg KOH/g. If a "PEG 400" COA shows a figure far outside that range, the grade is not what the label says. Our guide to reading a COA covers the other common lines: pH, moisture, colour and ash.
Pharma, cosmetic or industrial?
The chemistry is the same, but the controls are not. Pharma (IP/BP/USP) grades are tested for impurities such as ethylene glycol, diethylene glycol, ethylene oxide and 1,4-dioxane, and come with the documents regulators expect. Industrial grades do not need those limits. Never use an industrial grade in medicines, food contact or cosmetics. See IP vs BP vs USP grades.
Handling tips
- Liquid grades take up moisture from the air. Keep drums closed.
- Solid grades melt at about 55–65°C. Melt them gently in a water bath or jacketed vessel, not with direct flame.
- PEG is low in toxicity and not classed as hazardous for transport, but clean spills promptly because they are very slippery.
We supply polyethylene glycol (PEG 200/400/600/4000/6000) from Chennai. Tell us the grade and use, and we will match the documents.
Frequently asked questions
What does the number in PEG 400 mean?
It is the average molecular weight. PEG 400 has an average molecular weight of about 400, which makes it a clear liquid. Higher numbers such as 4000 and 6000 are waxy solids.
Is PEG 4000 the same as PEG 6000?
No. PEG 6000 has longer chains, so it melts a little higher and is harder. They overlap in uses such as tablet binders and ceramics, but formulations are usually built around one grade.
How do I check that I received the right PEG grade?
Check the hydroxyl value on the COA. Molecular weight ≈ 112,200 ÷ hydroxyl value. For PEG 400, the hydroxyl value should be about 265–295 mg KOH/g.
This article is general guidance. Always follow the Safety Data Sheet and your own site procedures for the specific product and grade you use.