Are Polyethylene Glycol and Ethylene Glycol the Same?

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Learn the key differences between Polyethylene Glycol (PEG) and Ethylene Glycol (EG), including chemical structure, CAS numbers, properties, applications, grades, pricing factors, and procurement considerations.

Key Takeaways

Ethylene Glycol (EG) and Polyethylene Glycol (PEG) are different chemicals and should not be used interchangeably.

Ethylene Glycol, also called Monoethylene Glycol (MEG), has CAS No. 107-21-1, molecular formula C₂H₆O₂, and molecular weight 62.07 g/mol.

Polyethylene Glycol is a polymer with repeating ethylene oxide/oxyethylene units and is commercially available in different molecular-weight grades.

EG is widely used in antifreeze, coolants, deicing fluids, polyester, and industrial applications.

PEG is widely used in pharmaceutical, cosmetic, personal-care, industrial, and formulation applications. FDA records list polyethylene glycol under

(CAS 25322-68-3) for specified food-related uses and technical effects.

For procurement, buyers should confirm CAS number, molecular weight, purity, grade, specifications, packaging, COA, SDS, and intended application before placing an order.

1. Are Polyethylene Glycol and Ethylene Glycol the Same?

No. Polyethylene Glycol (PEG) and Ethylene Glycol (EG) are different chemicals.

Although both names contain "ethylene glycol," their molecular structures, molecular weights, physical properties, applications, and purchasing specifications are different.

Quick Comparison

2. Chemical Structure and Properties

2.1 Ethylene Glycol (EG / MEG)

Ethylene Glycol is a low-molecular-weight diol with two hydroxyl groups. Its chemical name is ethane-1,2-diol, and its CAS number is 107-21-1. It has a molecular weight of 62.07 g/mol.

In international chemical trade, it is commonly called:

• Ethylene Glycol

Monoethylene Glycol (MEG)

• MEG Glycol
• MEG Mono Ethylene Glycol
• EG
• Ethane-1,2-diol

The term "ethanol glycol" is sometimes used in online searches, but it is not the preferred chemical name. Buyers should use Ethylene Glycol / Monoethylene Glycol and confirm CAS No. 107-21-1 when requesting quotations.

EG is widely used because of its low freezing point, relatively high boiling point, water miscibility, and heat-transfer properties. ATSDR identifies its major uses in antifreeze and deicing solutions, among other industrial applications.

2.2 Polyethylene Glycol (PEG)

Polyethylene Glycol (PEG) is not simply another name for ethylene glycol. PEG is a polymer containing repeating oxyethylene units.

Commercial PEG products are commonly identified by their approximate molecular weight, such as:

• PEG 200
• PEG 400
• PEG 600
• PEG 1000
• PEG 3350
• PEG 4000
• PEG 6000

The molecular weight has a major influence on PEG's viscosity, physical form, solubility, and end-use suitability.

3. Ethylene Glycol vs. Polyethylene Glycol: Main Differences

Chemical Structure

EG is a single small molecule, while PEG is a polymer made up of repeating units.

This structural difference explains why the two materials have very different physical properties and industrial applications.

Molecular Weight

EG has a fixed molecular weight of 62.07 g/mol. PEG does not have one fixed molecular weight because commercial PEG products are supplied in different molecular-weight grades.

Physical Form

Ethylene Glycol is normally supplied as a clear liquid. PEG may be supplied as a liquid, semisolid, or solid depending on molecular weight.

Toxicological Considerations

Ethylene Glycol requires careful handling because ingestion can cause serious poisoning and can damage the kidneys and other organs.

PEG is used in pharmaceutical and other formulation applications, but the specific PEG grade and applicable regulatory standard must always be verified for the intended use.

4. Applications of Ethylene Glycol

Ethylene Glycol is an important industrial raw material with applications across several sectors.

Antifreeze and Coolants

EG is widely used in automotive antifreeze and coolant formulations because of its freezing-point depression and heat-transfer properties.

For buyers searching for high quality ethylene glycol coolant, the material should be evaluated according to the requirements of the finished coolant formulation rather than price alone.

Polyester and PET Manufacturing

MEG is an important feedstock for producing polyester resins and PET-related materials.

Deicing Fluids

Ethylene Glycol is also used in deicing applications for aircraft and other systems.

Industrial Applications

Depending on grade and formulation, EG is also used in:

• Heat-transfer fluids
• Hydraulic brake fluids
• Inks
• Industrial formulations
• Synthetic fiber production
• Chemical manufacturing

5. Applications of Polyethylene Glycol

PEG is used across pharmaceutical, cosmetic, personal-care, and industrial applications.

Pharmaceutical Applications

Specific pharmaceutical grade polyethylene glycol products are used as excipients and formulation ingredients. FDA maintains an Inactive Ingredient Database for ingredients used in approved drug products.

For pharmaceutical procurement, buyers should confirm the required pharmacopeial standard, molecular-weight grade, impurity limits, manufacturing controls, and documentation.

Cosmetics and Personal Care

PEG grades are used in formulations such as:

• Creams
• Ointments
• Lotions
• Oral-care products
• Emulsions
• Formulation aids

Industrial Applications

Depending on molecular weight and specification, PEG can also be used as a lubricant, formulation aid, processing aid, or surfactant-related ingredient.

6. Ethylene Glycol Grades vs. Polyethylene Glycol Grades

Grade selection is one of the most important considerations for B2B buyers.

Industrial Grade Ethylene Glycol

For industrial applications, buyers commonly focus on:

• Assay/purity
• Water content
• Acidity
• Color
• Aldehydes
• Diethylene glycol (DEG)
• Packaging
• COA and SDS

High-Purity Ethylene Glycol

For applications requiring tighter specifications, buyers should request the manufacturer's complete TDS and COA rather than relying only on the product name.

Pharmaceutical Grade Polyethylene Glycol

PEG buyers should specify:

• PEG molecular weight
• Purity
• Viscosity where applicable
• Water content
• Residual impurities
• Applicable pharmacopeial standard
• Batch documentation
• GMP and quality-system information where required

A material should not be labeled pharmaceutical grade simply because it is chemically similar to a pharmaceutical material. WHO guidance emphasizes that materials from industrial or technical grades should not be designated as pharmaceutical grade without the required manufacturing conditions and quality system.

7. Procurement Guide: How to Buy EG or PEG

Before requesting a quotation, buyers should clearly define the following specifications.

For Ethylene Glycol / MEG

For Polyethylene Glycol

8. What Factors Affect Ethylene Glycol Price?

The ethylene glycol price quoted by suppliers can vary according to several factors:

• Purity and specification
• Industrial grade and application requirements
• Order quantity
• Packaging
• Origin and manufacturer
• Feedstock and energy costs
• Freight and destination
• Incoterms such as FOB, CFR, or CIF
• Market supply and demand

For bulk ethylene glycol purchases, logistics can have a significant impact on the delivered cost. Buyers should therefore compare suppliers on a consistent basis, such as CIF price per metric ton, rather than comparing product prices alone.

9. How to Select an EG or PEG Supplier

For B2B procurement, a competitive price is only one part of supplier evaluation.

A reliable supplier should be able to provide:

• Product specification and TDS
• Batch-specific COA
• SDS
• CAS number confirmation
• Packaging information
• Production and delivery lead time
• Export experience
• Quality-control information
• Sample availability where appropriate
• Clear payment and shipping terms

For higher-risk or regulated applications, buyers should also verify the supplier's quality system, manufacturing site, applicable certifications, traceability, and regulatory documentation.

This is particularly important for pharmaceutical and other sensitive supply chains. USP and WHO materials highlight the importance of controlling EG/DEG contamination and maintaining appropriate quality systems for pharmaceutical materials.

10. Frequently Asked Questions

Is Polyethylene Glycol the same as Ethylene Glycol?

No. Ethylene Glycol (EG/MEG) is a small diol with CAS 107-21-1, while Polyethylene Glycol (PEG) is a polymer with CAS commonly listed as 25322-68-3.

Is MEG the same as Ethylene Glycol?

Yes. MEG stands for Monoethylene Glycol, which is another commonly used name for Ethylene Glycol. Both refer to CAS No. 107-21-1.

Is PEG made from Ethylene Glycol?

PEG is produced through polymerization chemistry involving ethylene oxide and typically contains repeating oxyethylene units. It should not be treated as simply "liquid ethylene glycol with a higher molecular weight."

Can PEG be used instead of Ethylene Glycol in antifreeze?

Not automatically. EG and PEG have different molecular structures and physical properties. A coolant formulation must be designed and tested for the specific glycol being used.

What is Ethylene Glycol CAS 107-21-1?

Ethylene Glycol, CAS 107-21-1, is a low-molecular-weight diol with molecular formula C₂H₆O₂ and molecular weight 62.07 g/mol.

What is the CAS number of Polyethylene Glycol?

PEG is commonly identified by CAS No. 25322-68-3, although the exact commercial grade should also be identified by its molecular-weight designation. FDA lists PEG under this CAS number across specified molecular-weight ranges.

Is there food grade Ethylene Glycol?

Buyers should not assume that "food grade ethylene glycol" is an appropriate or recognized specification simply because the term appears in search results. Ethylene Glycol is toxic if ingested, and its use must be evaluated against the applicable regulatory requirements for the specific application.

What should I request when buying bulk Ethylene Glycol?

For a bulk quotation, provide CAS 107-21-1, required purity, grade, quantity, packaging or bulk transport method, destination port, Incoterm, and required documentation such as COA, SDS, and TDS.

11. Conclusion

Polyethylene Glycol and Ethylene Glycol are different materials with different chemical structures, properties, and applications. Ethylene Glycol, also known as Monoethylene Glycol (MEG), is primarily used in antifreeze, coolants, polyester production, deicing fluids, and other industrial applications. Polyethylene Glycol is a polymer available in different molecular-weight grades and is widely used in pharmaceutical, cosmetic, formulation, and industrial applications.

For procurement teams, the safest approach is to identify the material by chemical name, CAS number, molecular-weight grade where applicable, purity, intended application, and required quality standard. These details help prevent specification errors and make supplier quotations easier to compare.