PEG 200 vs 400 vs 600: Properties, Applications and Grade Selection

Shared chemistry, different molecular weight

PEG 200, PEG 400, and PEG 600 are all polyethylene glycols (CAS 25322-68-3) differing in average molecular weight and thus physical properties. The grade number indicates approximate average MW: PEG 200 ≈ 190–210 g/mol, PEG 400 ≈ 380–420 g/mol, PEG 600 ≈ 570–630 g/mol. All three consist of repeating –(OCH2CH2)– units terminated by hydroxyl groups.

All three are water-soluble, hygroscopic liquids at ambient temperature — but PEG 600 is more viscous and can appear waxy or semi-solid at cooler temperatures than PEG 200. As molecular weight increases within the liquid range, vapour pressure decreases, viscosity rises, and freezing point moves upward. These incremental changes drive distinct formulation behaviour even though the chemistry is identical.

Physical property comparison

PEG 200 — lightest liquid grade

PEG 200 is a colourless, non-volatile, hygroscopic liquid with the lowest viscosity of the three grades. It functions as a solvent, coupling agent, humectant, and defoaming aid. Applications include heat-transfer fluids, ink vehicles, fruit coatings, ceramic binders, and chemical intermediates for esterification or etherification reactions.

Its low viscosity makes it easy to pump, meter, and blend at ambient temperature. In multi-component systems, PEG 200 often acts as a co-solvent that improves compatibility between water and less polar ingredients. Because of its relatively higher vapour pressure compared to PEG 400, it is less common in open topical products where very low-MW glycols may be limited by monograph — formulators should verify pharmacopoeial acceptance for their specific grade and application.

PEG 400 — pharma and cosmetic workhorse

PEG 400 is more viscous than PEG 200 and widely used in pharmaceuticals as a solvent and solubilizer for actives that are poorly water-soluble. It appears in topical preparations, oral solutions, soft-gel fill liquids, and as a humectant in cosmetics and personal care products. Many pharmacopoeias list PEG 300 and PEG 400 (or macrogol 400) with defined limits on impurities.

In cosmetics, PEG 400 provides skin humectancy without the tackiness associated with some polyols. It is a common carrier in fragrance and essential oil dilutions. Industrial uses include hydraulic and brake fluids, metalworking lubricants, and as a plasticizer in adhesives. HP design-jet inks also use low-MW PEG as solvent and lubricant for print-head performance.

Avesta Pharma supplies pharmacopoeial-grade macrogol in this molecular weight range for regulated pharmaceutical markets. See our PEG in pharma formulations guide for stability considerations.

PEG 600 — intermediate semi-liquid

PEG 600 bridges liquid and semi-solid behaviour. At room temperature it is a viscous liquid; at lower temperatures it may thicken noticeably. It is used in adhesives, antistatic agents, mold-release agents, leather finishing, and as an intermediate for PEGylation in pharmaceutical research — where attachment of PEG chains to proteins or small molecules improves solubility and circulation time.

Slightly higher molecular weight improves film-forming tendency in some coating applications compared to PEG 400. In topical bases, PEG 600 can contribute body and substantivity. When blended with higher-MW solid PEG (e.g. PEG 4000), it helps tune the melting profile of suppository and ointment vehicles.

Application selection table

When to choose which grade

Select PEG 200 when low viscosity and maximum water compatibility matter — for example in industrial solvent systems where pharmacopoeial grade is not required. Choose PEG 400 for pharmaceutical solubilization, cosmetic humectancy, and applications where excipient monograph compliance is essential. Use PEG 600 when you need slightly higher body, melting characteristics, and film-forming tendency without moving to solid flakes (PEG 1500 and above).

Blending grades is a well-established strategy. A 50:50 mix of PEG 400 and PEG 4000, for instance, creates a semi-solid base with a melting point near skin temperature — ideal for topical delivery. Venus technical support can recommend blend ratios for specific melting point targets.

Venus manufactures PEG 200 through PEG 20000 from dedicated ethoxylation plants in India and the United States. See our full PEG range, manufacturing guide, and complete grades guide for higher molecular weight options.

How polyethylene glycol is manufactured

Polyethylene glycol is produced industrially by the ring-opening polymerization of ethylene oxide, initiated from water, ethylene glycol, or another short-chain alcohol under alkaline catalysis. The degree of polymerization — how many ethylene oxide units add to the growing chain before the reaction is stopped — determines the final average molecular weight, and therefore whether the product is labelled PEG 200, PEG 400, PEG 600, or a higher-molecular-weight solid grade. Because the polymerization is statistical rather than perfectly uniform, every PEG grade is technically a distribution of chain lengths clustered around the stated average molecular weight, which is why hydroxyl value titration rather than a single molecular weight number is the standard quality control test used to confirm grade identity.

This manufacturing process is essentially the same reaction used to produce fatty alcohol ethoxylates and other alkoxylates, except that PEG uses water or a simple glycol as the starter rather than a fatty alcohol — which is why PEG is fully water-soluble across its entire molecular weight range while fatty alcohol ethoxylates transition toward oil-solubility at low EO content. First developed as a commercial product in the early-to-mid twentieth century alongside the broader growth of ethylene oxide chemistry, PEG has since become one of the most widely used excipients in the pharmaceutical industry, valued for its low toxicity, water solubility, and the ability to fine-tune viscosity and melting behaviour simply by blending different molecular weight grades.

Global demand drivers for low molecular weight PEG

Liquid PEG grades see steady demand from pharmaceutical solubilization, personal care humectancy, and a wide range of industrial uses including textile lubricants, ceramics, and metalworking fluids. Because PEG is water-white, low in odour, and compatible with an unusually broad range of other ingredients, it frequently appears as a supporting or carrier ingredient rather than the headline active — meaning demand tracks the growth of the finished products it enables (topical pharmaceuticals, personal care serums, and specialty industrial fluids) more closely than any single end-use category.

This carrier-ingredient role also means PEG grade switches often go unnoticed by end consumers but matter greatly to manufacturing consistency. A formulator changing from PEG 400 to a blended PEG 300/PEG 600 system, for instance, needs to revalidate viscosity, active solubilization, and stability even though the finished product label may not change at all.

Quality and sourcing considerations

Even among liquid PEG grades, quality parameters matter. Hydroxyl number confirms molecular weight; moisture and residual ethylene oxide must meet application-specific limits. Pharmaceutical users should source from suppliers with GMP-aligned systems — Avesta Pharma for macrogol in regulated markets, Venus for technical and multi-compendial supply.

Request COA, TDS, and samples through our contact page. Our quality assurance team supports customer audits and method alignment.