Where to Buy Propylene Glycol: Grades, Specifications and Bulk Supply

The short answer

Propylene glycol is sold through completely different channels depending on how much you need and which grade you need.

• Litres — pharmacies, laboratory suppliers and online retailers sell 500 ml to 5 litre packs, usually USP grade, at a very high unit cost.
• Drums and IBCs — regional chemical distributors hold stock in 215 kg drums and 1,000 litre IBCs, with short lead times and moderate minimums.
• Tonnes — producers and merchant exporters supply full-container and bulk quantities against a specification, with longer lead times and a much lower unit cost.

The grade decision comes first, because it determines which of those channels can serve you at all, what documents you receive, and a large part of what you pay.

Propylene glycol is C₃H₈O₂ (propane-1,2-diol), CAS 57-55-6. It is a clear, colourless, nearly odourless, hygroscopic liquid, miscible with water in all proportions, with a relative density of about 1.036 at 20 °C and a boiling point around 187 °C. It is also traded as MPG (monopropylene glycol) — the same material under a different name.

Propylene glycol grades

Three grades cover almost all commercial demand. The chemistry is the same; the difference is impurity control and the documentation that proves it.

Industrial grade is the workhorse: unsaturated polyester resins, coolants, paints, de-icing fluids, functional fluids. It is made to a commercial specification set by the producer rather than to a pharmacopoeial monograph, and it carries no obligation to control glycol-family impurities to pharmacopoeial limits.

USP/EP grade is made and tested against the United States Pharmacopeia and European Pharmacopoeia monographs. The monographs have been tightened in recent years specifically around ethylene glycol and diethylene glycol, following WHO medical product alerts on contaminated liquid medicines: both now carry explicit limit tests for those two contaminants, determined by gas chromatography. Because these limits have been through accelerated revision, work from the edition of the monograph currently in force rather than from a figure quoted elsewhere. If you are formulating an oral, topical or parenteral product, this is not optional and the certificate of analysis must show the monograph tests, not a generic purity figure.

Food grade in practice usually means material meeting the Food Chemicals Codex specification. In the US, propylene glycol is affirmed GRAS under 21 CFR 184.1666 as a solvent, humectant, emulsifier, stabiliser and flavour carrier, with maximum use levels by food category. Much commercial material is dual-certified USP/FCC and sold as a single grade.

Do not over-specify, and do not under-specify

Buyers routinely ask for USP grade when the application is a resin, a coolant loop or a paint. That adds cost for documentation you will never use. If your product is industrial and there is no ingestion, inhalation or skin-contact pathway, industrial grade is the correct choice.

The reverse error is more serious. Industrial grade in a food, pharmaceutical, cosmetic or e-liquid application is not acceptable and is not a commercial judgement call — the impurity controls that make the material fit for those uses are precisely what industrial grade omits.

Propylene glycol vs ethylene glycol

These are different chemicals and they are not interchangeable.

Ethylene glycol is metabolised to toxic acid metabolites and ingestion is a medical emergency; poisoning cases are well documented and the material is handled accordingly. Propylene glycol is metabolised by a different route and has a long history of permitted use in food, medicines and cosmetics. The distinction matters enough that pharmacopoeial monographs for propylene glycol now include an explicit limit test for ethylene glycol as a contaminant.

The practical procurement risk is language. An enquiry that says only "glycol" — or "where to buy glycol" — does not identify a product. In the trade, "glycol" is used loosely for propylene glycol, ethylene glycol, diethylene glycol, triethylene glycol and dipropylene glycol. Always quote the CAS number. It is the one identifier that cannot be misread.

Related products you may see alongside PG:

• Dipropylene glycol (DPG), CAS 25265-71-8 — a mixture of isomers, used in fragrances, cosmetics and as a plasticiser and coalescing agent.
• Diethylene glycol (DEG), CAS 111-46-6 — an ethylene glycol derivative, toxic, and the contaminant of concern in pharmaceutical excipients.

MPG and DPG are traded side by side and the abbreviations are one character apart. Check the line item.

Applications by industry

Unsaturated polyester resins. One of the largest global end uses. Propylene glycol reacts with anhydrides to build the polyester backbone for glass-reinforced composites, gel coats, marine and construction laminates. Industrial grade.

Heat transfer and antifreeze. Propylene glycol solutions are chosen over ethylene glycol wherever a leak could reach food, drinking water or people — brewery and dairy cooling, food-plant chillers, HVAC in occupied buildings, solar thermal loops.

Pharmaceuticals. Solvent and co-solvent in oral liquids, topicals and some injectables; humectant in creams and ointments. USP/EP grade only.

Cosmetics and personal care. Humectant, solvent, viscosity modifier and carrier for actives; contributes freeze–thaw stability in emulsions.

Food and flavourings. Carrier solvent for flavours and colours, humectant in baked goods and confectionery, anticaking and processing aid, within the use levels set by regulation.

Tobacco and e-liquid. Humectant in tobacco processing and a carrier component in e-liquids. Pharmacopoeial or food grade material only.

Paints and coatings. Freeze–thaw stabiliser and open-time extender in water-based systems; also used in printing inks.

De-icing. Aircraft de-icing and anti-icing fluids and some runway and surface products, again where lower toxicity is required.

One regulatory point worth knowing: propylene glycol is prohibited in cat food in the United States under 21 CFR 589.1001, although it remains permitted in other animal feeds. If you supply pet food, check the destination market rules before specifying.

Handling, storage and shelf life

Hygroscopicity is the main practical issue. Propylene glycol absorbs atmospheric moisture readily. A drum left open, or an IBC repeatedly part-decanted in humid conditions, will drift above the 0.20% water limit that pharmacopoeial and most commercial specifications set. If your incoming QC is failing on water content, the cause is usually storage and handling, not the supplied material. Keep containers sealed; for pharmaceutical grade, nitrogen blanketing of bulk tanks is common practice.

Materials of construction. Stainless steel (304 or 316) is the standard for storage and transfer, particularly where colour and iron content matter. Galvanised or zinc-coated surfaces should be avoided. Carbon steel is used in some industrial service but can contribute colour and metal pickup. Confirm elastomer and gasket compatibility with your own engineering standards.

Fire. Propylene glycol is combustible rather than flammable — the closed-cup flash point is high, typically reported in the region of 100 °C. It burns, but does not present the vapour hazard of a solvent such as acetone or ethanol.

Transport classification. Propylene glycol is generally not classified as a dangerous good for transport under DOT, IMDG, IATA or ADR/RID, and is typically not classified as hazardous under CLP. This materially simplifies export documentation, packing and freight compared with most industrial chemicals. Always confirm against the current SDS for the specific material and the requirements of the destination country.

Shelf life. Producers commonly state a shelf life of around two years in sealed original packaging stored cool, dry and out of direct sunlight. Re-testing on receipt is normal for pharmacopoeial grade if material has been in store.

How to buy it properly

What to put in the enquiry

A specification-based enquiry gets a firm quote; a vague one gets a holding reply. Include:

1. Product name and CAS — propylene glycol, CAS 57-55-6, not "glycol".
2. Grade — industrial, USP/EP, or food/FCC. Say if you need dual USP/FCC certification.
3. Quantity and call-off pattern — one-off, or a monthly volume over a period.
4. Packing — 215 kg drums, 1,000 litre IBCs, flexitank or ISO tank.
5. Destination port and Incoterm — FOB, CFR, CIF or DAP, with the named port.
6. Documents required — see below.
7. End application — this lets a competent supplier tell you if you are over- or under-specifying.

Packing formats

• Drums — around 215 kg net in HDPE or steel; the standard for drum quantities, roughly 80 drums in a 20-foot container.
• IBCs — approximately 1,000 litres; convenient for plant handling, higher packing cost per tonne.
• Flexitanks — bulk liquid in a lined bladder inside a 20-foot container, typically around 20–24 tonnes; low packing cost, single-use.
• ISO tanks — bulk, dedicated, for regular large-volume receivers with tank storage.

Drum and container fill weights vary by producer and route; confirm exact figures at quotation.

Documents to ask for

Certificate of analysis against the stated specification, batch-specific. Safety data sheet in the format required by your jurisdiction. Certificate of origin. Packing list and bill of lading. For pharmacopoeial grade, additionally: confirmation of monograph compliance (USP, EP or both), the manufacturer's GMP or excipient GMP statement, and where required by the importing authority, a certificate of pharmaceutical product or manufacturer's declaration. Allergen, GMO, BSE/TSE, halal and kosher statements are routinely requested for food and pharmaceutical use.

Comparing quotes

Compare on landed cost per tonne of product, not price per drum — packing type, fill weight, freight and duty move the number more than the unit price does. Then compare the specification line by line, and check that the certificate of analysis actually reports the tests you need rather than a summary. A cheaper industrial-grade offer against a USP requirement is not a cheaper offer.

Where to buy: the four channels

Retail and pharmacy. Best for litres. You get immediate availability and no minimum, at the highest unit cost by a wide margin, and often without a batch-specific certificate of analysis. Suitable for laboratory and trial quantities, not for production.

Chemical distributors. Best for drums and IBCs within a country or region. Stock is local, lead times are days, and technical support is available. Minimums are typically one drum. Price carries the distributor's stockholding and repackaging cost, and the certificate of analysis is usually the original producer's.

Producers direct. Best for consistent large volumes. Lowest unit cost and the fullest documentation, including direct GMP and audit access for pharmaceutical grade. Minimums are high — often a full ISO tank or a full container — and commercial terms suit committed annual offtake rather than variable demand.

Merchant exporters from India. Best for buyers importing container quantities who want a single point of accountability across sourcing, quality documentation and shipping. An export house works with qualified manufacturers, consolidates mixed-chemical orders into one container, and handles export documentation, inspection and freight. The trade-off is that you are relying on the exporter's supplier qualification, so ask which manufacturer the material comes from, whether the plant is audited, and what happens on a specification failure. Lead times include ocean transit, so this channel suits planned requirements rather than emergencies.

There is no single right answer. A formulator needing 20 litres of USP grade next week should call a distributor. A resin plant taking 200 tonnes a year should be talking to producers and exporters.

Enquiries

Propylene glycol (MPG), CAS 57-55-6, in industrial, USP/EP and food grades is supplied by Scapex Exports against the buyer's specification, in drums, IBCs and bulk formats. Manufacturing source and country of origin are confirmed in writing at quotation.

Send your grade, quantity, packing preference, destination port and required documents, and you will receive a specification-matched quotation.

Frequently asked questions