Mono Propylene Glycol CAS 57-55-6
Chelora Chemicals supplies USP, food and industrial grade mono propylene glycol to pharmaceutical, food, personal care, resin and coolant users worldwide. Every consignment leaves with a batch-specific COA covering purity, water, DPG content and colour, the current SDS and full export documentation.
Also known as: MPG · Propylene glycol · 1,2-Propanediol · PG · Methyl ethylene glycol
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Price, lead time and a sample COA for Mono Propylene Glycol, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (purity, water, DPG, colour)
- Safety Data Sheet (SDS)
- Transport and export documents
- Third-party inspection on request
- Certificate of origin
What is Mono Propylene Glycol?
Mono propylene glycol is a C3 diol, C₃H₈O₂, a clear, colourless, nearly odourless and slightly viscous liquid that is completely miscible with water.
Its defining commercial property is low toxicity. Unlike ethylene glycol, MPG is generally recognised as safe for food use and is accepted in pharmaceuticals and cosmetics, which opens applications no other glycol can serve.
It is made by hydrating propylene oxide, with a growing bio-based share produced by hydrogenolysis of glycerine or sugars.
Uses span unsaturated polyester resins, food and pharmaceutical formulation, personal care humectancy, antifreeze where toxicity matters, aircraft deicing, e-liquids and heat transfer fluids.
Why Mono Propylene Glycol specifically
- Low toxicity. Accepted as a food additive and pharmaceutical excipient, which ethylene glycol can never be.
- A humectant. Holds moisture in foods, cosmetics and tobacco products.
- A good solvent for actives. Dissolves flavours, fragrances and many pharmaceutical actives.
- Freeze protection. Depresses freezing point effectively where a non-toxic coolant is required.
How Mono Propylene Glycol is Manufactured
MPG is made by hydrating propylene oxide, with bio-based routes growing from glycerine and sugar feedstocks.
- Propylene oxide feed. PO from an epoxidation unit is the conventional starting material.
- Hydration. PO and excess water react thermally at about 200 °C, or catalytically at lower temperature.
- Co-product formation. Dipropylene and tripropylene glycol form alongside MPG, with the ratio set by the water excess.
- Evaporation. Excess water is removed in an evaporator train.
- Vacuum distillation. MPG is separated from DPG and TPG and purified to grade.
- Bio-based routes. Hydrogenolysis of glycerine or sorbitol gives chemically identical MPG from renewable feedstock.
Typical Commercial Specification
Figures below are representative of USP and EP grade MPG. Industrial grade carries wider limits — tell us the application and we will send the matching sheet.
| Parameter | Typical Value |
|---|---|
| Appearance | Clear colourless viscous liquid, practically odourless |
| MPG purity | 99.5% min by weight (99.8% for USP) |
| Water content | 0.2% max |
| Dipropylene glycol | To grade, typically 0.3% max |
| Acidity (as acetic acid) | To grade, typically 10 ppm max |
| Residue on ignition | 0.007% max (USP) |
| Heavy metals | 5 ppm max (USP) |
| Chlorides and sulphates | To pharmacopoeial limits |
| Colour (Pt-Co) | 10 max |
| Specific gravity at 20/20 °C | 1.0360 to 1.0380 |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C₃H₈O₂ (CH₃CH(OH)CH₂OH) |
| Molecular weight | 76.09 g/mol |
| Appearance | Clear colourless viscous liquid, faintly sweet taste |
| Boiling point | 188 °C |
| Melting point | −59 °C |
| Flash point | About 104 °C (closed cup) |
| Density | 1.036 g/cm³ at 20 °C |
| Viscosity | About 56 mPa·s at 20 °C |
| Vapour pressure | About 0.011 kPa at 20 °C |
| Solubility in water | Completely miscible |
| Hygroscopicity | Strongly hygroscopic |
| Freezing protection | A 50% aqueous solution protects to about −33 °C |
| Incompatibilities | Strong oxidisers, strong acids and bases at high temperature |
Behaviour in the process
MPG is stable and forgiving, with a few behaviours that matter in formulation:
- Strongly hygroscopic. Absorbs water from air, which is the basis of humectant use and a nuisance where water specification is tight.
- More viscous than MEG. At about 56 mPa·s it pumps more slowly, especially in cold weather.
- Microbiologically supportive when dilute. Diluted solutions can support growth; concentrated MPG is self-preserving.
- Oxidises slowly at temperature. Air exposure when hot raises acidity and can cause colour.
MPG Grades and Alternatives
MPG is bought by grade certification first and by numerical specification second, because the regulated applications demand it.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| USP / EP grade MPG | Pharmacopoeial certified | Pharmaceutical, food, personal care and e-liquid applications |
| Food-grade MPG | FCC compliant | Food flavouring, humectant and processing aid use |
| Industrial-grade MPG | 99.5%+, no pharmacopoeial certification | Resins, coolants, deicing and industrial formulation |
| Bio-based MPG | From glycerine or sugar | Where renewable content certification is required |
| Mono ethylene glycol | C₂ diol, CAS 107-21-1 | Cheaper and better as a coolant, but toxic and never for human contact |
Stated plainly: where there is human contact, MPG replaces MEG and the price difference is irrelevant. Where there is not, MEG usually performs better as a heat transfer fluid at lower cost.
Industries We Supply Mono Propylene Glycol To
MPG reaches more regulated industries than any other glycol, which is why grade certification dominates the conversation.
Where Mono Propylene Glycol is Used
Unsaturated polyester resins take the largest industrial share, while food, pharmaceutical and personal care applications take the premium volume.
In pharmaceutical and food use
MPG dissolves actives and flavours, holds moisture and suppresses microbial growth at higher concentrations. The regulated applications turn on documentation as much as chemistry: pharmacopoeial testing, batch traceability, GMP declarations and residual solvent data are all expected, and a lot without them cannot be used however pure it is.
In unsaturated polyester resins
MPG is the standard diol in general-purpose UPR, reacting with phthalic and maleic anhydride to form the polyester backbone that styrene later crosslinks. Its methyl group disrupts crystallinity, giving a resin that stays soluble in styrene — which is exactly why it is preferred over ethylene glycol here.
Need a specific grade, purity and packing format?
Tell us the grade, the grade certification and purity your application requires, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis, with pharmacopoeial testing documented in full for USP and EP grades.
- MPG purity and water content — by gas chromatography and Karl Fischer titration.
- Dipropylene glycol content — reported because it affects resin and formulation behaviour.
- Acidity — measured as a degradation and storage indicator.
- Residue on ignition and heavy metals — tested to pharmacopoeial limits for USP and EP grades.
- Colour and odour — confirming freedom from contamination, critical for food and personal care.
- Identity tests — specific gravity, refractive index and IR identity for regulated grades.
Common Process Problems & Likely Causes
When MPG causes trouble, it is usually water pick-up, DPG content, odour or missing documentation. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Water content high on arrival | Hygroscopic pick-up from humid air or a wet container | Water result, container seal and storage conditions |
| Odour in a food or cosmetic product | Trace impurities or contamination in transfer | Odour test, colour and container history |
| Resin properties off target | DPG content or water shifting the diol balance | DPG and water figures against the previous COA |
| QA rejecting the lot in a regulated chain | Grade certification missing or incomplete | Pharmacopoeial certificate, GMP declaration and traceability |
| Microbial growth in a diluted solution | Dilution below the self-preserving concentration | Working concentration and system hygiene |
| Pumping difficulty in cold weather | Viscosity rising below about 10 °C | Storage temperature and pump sizing |
Packaging, Storage & Shipping
- Standard packing. 200 L drums, 1000 L IBCs, flexitanks, ISO tank containers and bulk parcel cargoes.
- Moisture control. MPG is strongly hygroscopic; keep containers sealed and use dry breathers where water specification matters.
- Material compatibility. Stainless steel preferred for food and pharmaceutical grades; carbon steel acceptable for industrial use but contributes colour.
- Hygiene. For food and pharmaceutical grades, dedicated lines, pumps and tanks are expected, with cleaning records.
- Temperature. Ambient storage; viscosity rises noticeably in cold weather.
- Segregation. Keep apart from oxidisers and, critically, from ethylene glycol and DEG to prevent mix-ups.
- Shelf life. Typically 24 months in sealed storage. Water content and colour are the practical checks.
- Transport classification. Not classified as dangerous goods for transport.
Hazards & Safe Handling
MPG has very low toxicity and is accepted in food and pharmaceutical use. It is not classified as dangerous goods and presents only mild irritant concerns in normal handling.
- Low toxicity. Generally recognised as safe for food use and accepted as a pharmaceutical excipient. Not classified as harmful in normal handling.
- Mild irritation. Can cause mild eye and skin irritation on prolonged contact. Use gloves and eye protection for routine handling.
- Low flammability. Flash point above 100 °C; not a flammable-liquid hazard in ordinary handling, though it will burn in a fire.
- Sensitive individuals. A small proportion of people show contact sensitivity to propylene glycol in topical products.
- Hot handling. Heat transfer systems operate hot; thermal burns are the realistic process hazard.
- Environment. Readily biodegradable; still contain spills to prevent oxygen depletion in watercourses.
Regulatory & Compliance Notes
MPG is unregulated for transport but subject to extensive food and pharmaceutical standards. The notes below are orientation rather than legal advice.
- GHS classification. Not classified as hazardous in most jurisdictions.
- Food additive status. Approved as a food additive in the EU (E1520), the US and most other markets, with FCC specifications applying.
- Pharmacopoeial standards. USP, EP, BP and JP monographs all cover propylene glycol, with identity, purity, heavy metal and residue requirements.
- DEG contamination testing. Regulators require identity and DEG limit testing of every container entering pharmaceutical manufacture, following historical substitution incidents.
- Transport. Not classified as dangerous goods. Standard bulk and packaged cargo documentation applies.
- REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
We Supply Mono Propylene Glycol Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Mono Propylene Glycol from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork 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 ports arranged where routing and cargo rules allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
- Flexible volumes. From a pallet of drums up to repeat bulk shipments 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 Mono Propylene Glycol from Chelora
We are an independent sourcing and supply partner. For MPG that means settling three things at enquiry: the grade and certification your chain requires, whether bio-based content is needed, and the packing and dedicated-equipment arrangements for food or pharmaceutical use.
- Documentation on every lot. Batch-specific COA (purity, water, DPG, colour), plus SDS and the full transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. From a pallet of drums through to full bulk shipments on contract supply.
- Grade matching. USP, EP, food or industrial grade, with bio-based options where renewable content certification is required.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. Propylene Oxide, Mono Ethylene Glycol, Diethylene Glycol and other feedstocks alongside Mono Propylene Glycol from one supplier.
How ordering works
- Send the enquiry. Product, grade or purity, 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 format and a sample COA, normally within one working day.
- Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.
Mono Propylene Glycol — Common Questions
The questions our technical desk is asked most often about Mono Propylene Glycol. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of mono propylene glycol?
The CAS number for MPG is 57-55-6, and its EC number is 200-338-0. Its molecular formula is C₃H₈O₂ with a molecular weight of 76.09 g/mol, and it is classified under HS code 2905.32.
What is MPG used for?
For unsaturated polyester resins, pharmaceutical and food formulation, personal care products, non-toxic antifreeze and coolants, aircraft deicing fluids, e-liquids and heat transfer systems.
Do you supply MPG worldwide?
Yes. Chelora Chemicals supplies and exports MPG worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India, in USP, food and industrial grades.
What is the difference between USP and industrial grade MPG?
USP and EP grades carry documented pharmacopoeial testing — identity, heavy metals, residue on ignition, DEG limits — plus GMP and traceability documentation. Industrial grade meets a numerical specification only and cannot be used in a regulated chain.
Is MPG safe for food use?
Yes, within approved limits. It is an approved food additive in the EU as E1520 and in the US and most other markets, provided the material is food or pharmacopoeial grade with the proper certification.
How is MPG manufactured?
By hydrating propylene oxide with excess water, thermally or catalytically, with dipropylene and tripropylene glycol as co-products. Bio-based MPG is made by hydrogenolysis of glycerine or sugars and is chemically identical.
What is the difference between propylene glycol and ethylene glycol?
MPG has very low toxicity and is accepted for food, pharmaceutical and cosmetic use; MEG is acutely toxic and must never contact anything consumed. MEG is cheaper and a slightly better heat transfer fluid.
Is MPG hazardous?
No, in normal handling it is among the least hazardous products we supply. It is not classified as dangerous goods for transport and presents only mild irritant concerns.
How should MPG be stored?
In clean, sealed, preferably stainless containers with dry breathers, since MPG is hygroscopic. For food and pharmaceutical grades, dedicated lines and tanks with cleaning records are expected.
Why must MPG be stored separately from DEG?
Because the three glycols look identical and substitution of DEG for propylene glycol in medicines has caused mass fatalities. Physical separation, clear labelling and independent identity testing are the established controls.
What packing sizes and order quantities are available?
200 L drums, 1000 L IBCs, flexitanks, ISO tank containers and bulk parcel cargoes. Orders run from a pallet of drums up to repeat bulk cargoes on contract supply.
Is bio-based MPG available?
Yes. MPG made by hydrogenolysis of glycerine or sugars is chemically identical to the petrochemical product and carries renewable content certification where that is required.
Ready to source Mono Propylene Glycol?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.