Polyethylene Glycol (PEG 400/4000/6000) CAS 25322-68-3

What is Polyethylene Glycol (PEG 400/4000/6000)?

Polyethylene glycols are polymers of ethylene oxide, H(OCH₂CH₂)_nOH, named by their average molecular weight. The number in the name is the whole specification in miniature: PEG 400 is a clear viscous liquid, PEG 4000 is a waxy solid, PEG 6000 is a harder solid, and they differ in nothing but chain length.

That one variable gives a remarkable spread of function. The liquid grades act as solvents and co-solvents for poorly soluble drugs, as softgel fill vehicles and as plasticisers in film coating. The solid grades build suppository and ointment bases, carry drugs in melt-based solid dispersions, and act as binders and lubricants in tablets.

All grades are water-soluble, hygroscopic, non-volatile and well tolerated, with a long history of oral, topical and parenteral use. They are also chemically simple and largely unreactive, which is why they appear in so many formulations where something inert is needed to carry an active.

The important caveats are residuals and oxidation. Ethylene oxide and 1,4-dioxane from manufacture are limited on toxicological grounds, and PEGs oxidise slowly in storage to peroxides, aldehydes and acids — which is the one way an inert excipient can quietly destabilise a drug product.

Why polyethylene glycol specifically

• One chemistry across liquid and solid. Changing molecular weight moves you from a solvent to a suppository base without changing excipient families or regulatory position.
• Soluble in water and in organics. Which is what lets it carry poorly soluble actives and still release them into aqueous media.
• Non-volatile and well tolerated. Unlike the volatile co-solvents, it stays where it is put, and it has a long safety record across routes of administration.
• Blendable grades. Mixing a liquid and a solid grade gives an intermediate consistency, so a suppository or ointment base can be dialled to a target melting behaviour.

How PEG is Manufactured

Polyethylene glycols are made by polymerising ethylene oxide onto a starter molecule. The degree of polymerisation sets the grade, and the residuals from the process set the specification.

• Anionic ring-opening polymerisation. Ethylene oxide is polymerised onto water or ethylene glycol with an alkaline catalyst. The monomer-to-starter ratio determines the average chain length and therefore the grade.
• Molecular weight control. Average molecular weight is confirmed by hydroxyl value rather than measured directly — which is why the hydroxyl value appears on the certificate and effectively defines the grade.
• Catalyst removal and neutralisation. The alkaline catalyst is removed or neutralised. Residual alkalinity affects pH and long-term stability.
• Residual stripping. Unreacted ethylene oxide and 1,4-dioxane formed as a by-product are stripped to the low limits the monographs require.
• Finishing. Liquid grades are filtered and drummed; solid grades are flaked, prilled or powdered according to the form required.

Typical Commercial Specification

Figures below are representative of pharmacopoeial PEG 400. PEG 4000 and 6000 differ in physical form, melting range and hydroxyl value — tell us the grade or the application and we will quote against it.

Physical & Chemical Properties

Behaviour in the formulation

PEG is chosen for being unreactive, and mostly it is. Five behaviours shape how it is used:

• Solubilisation. Liquid grades dissolve many poorly soluble drugs that water will not, which is the basis of their use in softgel fills and oral liquids.
• Melting and solidification. Solid grades melt in a convenient range, so a drug can be dissolved or dispersed in the melt and cast — the mechanism behind PEG suppository bases and melt solid dispersions.
• Plasticisation. Added to a film coating system, PEG makes the film flexible enough to survive handling without cracking.
• Hygroscopicity. It attracts water, which is useful in some ointment bases and a problem in moisture-sensitive formulations.
• Oxidative degradation. Over time and with heat, light or metal contact, PEG forms peroxides, aldehydes and acids. These can oxidise susceptible actives and lower the pH of a formulation — the main way a supposedly inert excipient causes a stability failure.

PEG Grades and the Alternative Vehicles

Within PEG the choice is molecular weight, which is really a choice of physical state. Between vehicles it is about solvency, tolerability and what happens at body temperature.

Stated plainly: the grades are a consistency scale, and formulators routinely blend across it. A suppository base is often a mixture of a liquid and a solid grade chosen to melt and release at the right rate, which is a far more flexible approach than any single grade allows.

Industries We Supply PEG To

The same chemistry goes to a softgel line, a suppository plant and a coating pan. What changes between them is the grade, the residual limits and the documentation each sector expects.

Where PEG is Used

PEG is bought for its physical state as much as its chemistry, which is why most buyers take more than one grade. These are the end uses our customers buy it for.

In solubilisation and softgels

PEG 400 dissolves a wide range of poorly soluble drugs and is miscible with water, so a fill solution stays a solution and then disperses when the capsule opens. It is a mainstay of softgel fills and oral liquid formulation. The practical limits are hygroscopicity, which can draw water through a softgel shell over time, and oxidative degradation, which both lowers pH and generates species capable of attacking a sensitive active.

In suppositories and topical bases

PEG suppository bases work differently from fatty bases: instead of melting at body temperature they dissolve in the mucosal fluid, which gives a different release profile and avoids the storage temperature sensitivity that fatty bases have. Formulators blend liquid and solid grades to set the hardness and dissolution rate, which is why a suppository plant usually buys two or three grades rather than one.

In melt solid dispersions

Dissolving a poorly soluble drug in molten PEG and cooling gives a solid dispersion in which the drug is finely divided or amorphous, and so dissolves faster. PEG 4000 and 6000 are the usual carriers because their melting ranges are convenient and they solidify cleanly. The weakness relative to polymer carriers like povidone is that PEG is crystalline, so it stabilises the amorphous state less effectively over long shelf lives.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis written against the monograph you nominate, with the residual figures that matter toxicologically reported alongside the identity tests.

• Hydroxyl value and average molecular weight — the compendial grade identifier, and the figure to compare between lots and suppliers.
• Ethylene oxide and 1,4-dioxane — toxicological limits from the manufacturing route, tested specifically.
• Ethylene glycol and diethylene glycol — controlled as a total, an important limit given the history of glycol contamination incidents.
• Peroxides and formaldehyde — oxidative degradation markers, critical where the active is oxidation-sensitive.
• Water content — Karl Fischer. The material is hygroscopic, so this moves with storage.
• pH, viscosity and freezing or melting range — physical confirmation of grade and of residual alkalinity.
• Heavy metals and sulphated ash — elemental impurity and residue control.

Common Process Problems & Likely Causes

When PEG causes trouble in a formulation, it is usually oxidation or a grade and moisture question. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. 220 kg net drums and IBCs for PEG 400; 25 kg bags or drums of flakes, prills or powder for PEG 4000 and 6000.
• Oxidation control. PEG generates peroxides in storage. Keep containers sealed, store cool and out of light, and nitrogen-blanket bulk liquid storage where the application is oxidation-sensitive.
• Storage. Cool, dry and well-ventilated, away from oxidising agents and sources of heat. Cool storage materially slows peroxide formation.
• Hygroscopicity. All grades take up water, the liquid grades most readily. Keep containers closed and minimise headspace.
• PEG 400 freezing point. It solidifies at around 4 to 8 °C, so drums in a cold warehouse arrive solid. Warm gently and homogenise before use — do not overheat, which accelerates oxidation.
• Materials of construction. Stainless steel or lined vessels. Avoid prolonged contact with bare iron and copper, which catalyse oxidation.
• Shelf life. Typically 24 to 36 months in unopened original packing under those conditions. For oxidation-sensitive products, re-test peroxides rather than relying on the original certificate.
• Transport classification. Not classified as a dangerous good for transport.

Hazards & Safe Handling

Polyethylene glycols are among the best-tolerated excipients in use, with a long record across oral, topical and parenteral products. The handling considerations are physical, with the main chemical points concerning residuals rather than the polymer itself.

• Slip hazard. Spilled PEG, liquid or molten, is extremely slippery. Clean spills promptly and completely — this is the most common incident associated with the material.
• Hot melt handling. Solid grades are often melted for processing. Molten PEG causes thermal burns and clings to skin; handle with heat-resistant gloves and face protection.
• Residual ethylene oxide. Controlled to 1 ppm in pharmaceutical grades. The polymer itself is not a concern, but the residual is, which is why the limit exists and why it should be on your specification.
• Eye contact. Mild mechanical and chemical irritation. Safety glasses during transfer.
• PPE. Gloves, safety glasses and normal plant workwear for ambient handling; heat protection where molten material is involved.
• Dust. Powdered solid grades present the usual fine organic powder dust and explosion considerations.
• Spill response. Contain and absorb with inert material. Expect the area to remain slippery until thoroughly cleaned with detergent.
• Environment. Low aquatic toxicity and readily handled by conventional treatment, but do not discharge quantities to drain. Dispose in line with local regulations.

Regulatory & Compliance Notes

Polyethylene glycols are compendial excipients with monographs in all the major pharmacopoeias, used across oral, topical and parenteral products. Because obligations differ by territory and use, the notes below are orientation rather than legal advice — confirm your own position with your regulatory adviser.

• Pharmacopoeial status. Monographs in IP, BP, Ph. Eur. (as macrogols) and USP-NF. We supply against the monograph you nominate, with a compliance statement on the COA.
• Glycol impurity scrutiny. Ethylene glycol and diethylene glycol limits attract close regulatory attention across the industry following contamination incidents in other glycol-based excipients. Expect these figures to be checked, and keep the traceability documentation.
• Residual ethylene oxide and dioxane. Both are controlled on toxicological grounds at ppm levels and are standard compendial tests for pharmaceutical grades.
• Grade on the filing. The PEG grade is normally named in a marketing authorisation, particularly where it forms a suppository base or a solid dispersion carrier, so changing grade is a variation.
• Food and cosmetic use. Permitted in food and cosmetic applications in the major regulatory systems, within the conditions that apply in your market.
• Excipient GMP expectations. Supply chains for compendial excipients increasingly expect documented GMP and supplier qualification. Tell us what your quality agreement requires.

We Supply PEG Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Polyethylene Glycol (PEG 400/4000/6000) from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, pharmacopoeial documentation and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other Indian ports arranged where it suits the routing.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the ethylene oxide, dioxane and glycol impurity data issued as a complete set.
• Flexible volumes. A single drum or bag for laboratory qualification, through LCL consolidations, up to repeat full loads on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying PEG from Chelora

We are an independent sourcing and supply partner. For PEG that means settling two things at enquiry: the grade, or the consistency and melting behaviour you need if you are blending, and whether your active is oxidation-sensitive — because that decides how tightly the peroxide figure needs controlling.

• Documentation on every lot. Batch-specific COA written against the nominated monograph, with hydroxyl value, residuals and glycol figures reported, plus SDS and TDS.
• Samples before commitment. Trial quantities for formulation qualification ahead of a commercial order.
• Quantities. From a single drum or bag through to tank and full container quantities on contract supply.
• Grade range. PEG 400, 1500, 4000 and 6000, with intermediate grades sourced on request.
• Export experience. Packing, labelling and export documentation handled for sea and air freight.
• Related excipients. MCC, lactose monohydrate, povidone, HPMC and gelatin from one supplier.

How ordering works

• Send the enquiry. Product, grade or pharmacopoeia standard, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing and a sample COA, normally within one working day.
• Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
• Ship and document. Packed, labelled and loaded with the full export document set, and tracked through to arrival.

Related Pharmaceutical Excipients & Intermediates

Buyers of PEG usually source several of these alongside it. Consolidating them on one order cuts freight cost and gives you a single point of contact for documentation.