Acrylic Acid
The monomer inside every disposable nappy. It also freezes at 13 °C, and because the inhibitor stays behind in the liquid when it does, a frozen drum is an uninhibited one.
Molecular Structure
What is Acrylic Acid?
Acrylic acid is the simplest unsaturated carboxylic acid — a vinyl group directly attached to a carboxyl. Both ends work. The double bond polymerises under free radical conditions; the acid group can be neutralised to a salt, esterified to an acrylate, or left in place to give the polymer its water absorbency and its ability to hold ions.
Production is by two-stage catalytic oxidation of propylene. The first reactor takes propylene to acrolein over a bismuth-molybdenum catalyst; the second oxidises acrolein to acrylic acid over molybdenum-vanadium. Propane-based and bio-based routes exist but remain small.
The largest single outlet is superabsorbent polymer, made by neutralising acrylic acid to sodium acrylate and crosslinking it into a network that holds many times its own weight in liquid. The rest is split between acrylate esters for adhesives, paints and textiles, and polyacrylic acid for detergents, dispersants and water treatment.
Acrylic acid freezes at 13 °C, and that is a safety issue rather than an inconvenience. The MEHQ inhibitor is excluded from the crystal lattice as the acid solidifies, so the frozen material is effectively uninhibited while the liquid pocket around it becomes over-inhibited. Thawing must be slow, complete and fully mixed — localised heating of a frozen container has caused runaway polymerisations.
Quick Reference
Key Physical & Chemical Properties
Structure & Bonding
A vinyl group conjugated directly with a carboxylic acid. The conjugation activates the double bond towards polymerisation and makes acrylic acid noticeably more acidic than a saturated equivalent — and both of those properties are used in every downstream product.
Skeletal structure — vinyl group conjugated with a carboxyl
Structural Identity
- IUPAC NameProp-2-enoic acid
- Common namesAcrylic acid, AA, GAA, vinylformic acid
- Molecular FormulaC₃H₄O₂
- Molecular Weight72.06 g/mol
- Functional groupsVinyl double bond, carboxylic acid
- AciditypKa 4.25
- InhibitorMEHQ — requires dissolved oxygen
- Freezing behaviourExcludes inhibitor on crystallising
- Made fromPropylene → acrolein → acrylic acid
- CAS Number79-10-7
- InChI KeyNIXOWILDQLNWCW-UHFFFAOYSA-N
Product Specifications
Chelora supplies Acrylic Acid in standard and custom grades. Contact us for specification sheets tailored to your process.
| Chemical name | Acrylic acid, glacial |
|---|---|
| CAS Number | 79-10-7 |
| Molecular formula | C₃H₄O₂ |
| Molecular weight | 72.06 g/mol |
| Purity (min) | ≥ 99.50 wt% |
| MEHQ inhibitor | 180 – 220 ppm wt |
| Water (max) | ≤ 0.15 wt% |
| Acetic acid (max) | ≤ 0.05 wt% |
| Propionic acid (max) | ≤ 0.05 wt% |
| Diacrylic acid (dimer, max) | ≤ 0.10 wt% |
| Furfural (max) | ≤ 5.0 ppm wt |
| Benzaldehyde (max) | ≤ 2.0 ppm wt |
| Total aldehydes as furfural (max) | ≤ 10 ppm wt |
| Maleic anhydride (max) | ≤ 5.0 ppm wt |
| Iron (max) | ≤ 0.20 ppm wt |
| Colour (max) | ≤ 10 Pt-Co (Hazen) |
| Freezing point (min) | ≥ 12.5 °C |
| Recommended storage | 15 – 25 °C, oxygen present in vapour space |
| Flash point | 50 °C (closed cup) |
| Autoignition temperature | 395 °C |
| Transport classification | UN 2218, Class 8 with 3 subsidiary, PG II, stabilized |
Downstream Applications & Derivatives
Key derivative chains and industrial uses of Acrylic Acid.
Superabsorbent Polymers
The largest outlet. Neutralised to sodium acrylate and crosslinked into a network that absorbs many times its weight in liquid — baby nappies, adult incontinence and feminine hygiene products.
Acrylate Esters
Butyl, ethyl, methyl and 2-ethylhexyl acrylate for pressure-sensitive adhesives, architectural and industrial coatings, textile binders and leather finishing.
Detergent Polymers
Polyacrylic acid and acrylic-maleic copolymers as anti-redeposition agents and builders in laundry and dishwash formulations, replacing phosphates.
Water Treatment
Scale inhibitors and dispersants for cooling water, boiler feed, reverse osmosis and oilfield service, where the carboxyl groups sequester hardness ions.
Rheology Modifiers
Crosslinked polyacrylic acid thickeners for cosmetics, pharmaceutical gels, paints and printing pastes — high viscosity at very low solids.
Construction & Paper
Superplasticisers for concrete, dry-mix mortar redispersible powders, and paper coating binders and retention aids.
Why source Acrylic Acid through Chelora Petrochem?
Verified Origin
Full origin certification and asset-backed supply chain documentation — no grey-market supply.
Grade Flexibility
Glacial and ester-grade acrylic acid supplied. We certify MEHQ as measured plus dimer content, because those two figures together tell you how much usable shelf life the material actually has.
Full Documentation
CoA, SDS, UN 2218 transport documents, REACH compliance, and destination-market certificates with every shipment.
Logistics Support
Experienced in inhibited corrosive monomer logistics — temperature-controlled ISO tanks and road tankers with oxygen-controlled vapour space, plus drums and IBCs, for Indian and international delivery.
Storage & Handling Guidelines
Always refer to the full SDS before handling. The following is a summary of key requirements.
- Hold storage between 15 and 25 °C. That window is narrow for a reason — below about 13 °C the acid freezes and separates from its inhibitor, and above 25 °C dimerisation and inhibitor consumption both accelerate.
- Never apply localised heat to frozen or partially frozen acrylic acid. Thaw the whole container slowly at no more than 35 °C, with circulation or mixing, and homogenise fully before use so the inhibitor is redistributed.
- Maintain oxygen in the vapour space. MEHQ needs dissolved oxygen to work, so storage is under air or nitrogen with controlled oxygen content — never a pure nitrogen blanket.
- Test inhibitor level, dimer content and storage temperature on a defined schedule, and rotate stock. Dimer formation is irreversible and is the clock running on the material.
- Use 316 stainless steel or a suitably qualified lining throughout. Acrylic acid is corrosive to carbon steel, and dissolved iron both discolours the acid and catalyses polymerisation.
- Exclude peroxides, strong oxidisers, strong bases, amines and free-radical initiators. Contact with alkali is strongly exothermic and can initiate polymerisation directly.
- Bund all storage and prevent release to drains or surface water. Acrylic acid is very toxic to aquatic life and will acidify receiving water as well.
- Provide safety showers and eyewash within immediate reach of every transfer point. The acid is corrosive and causes severe burns on contact.
- Have a written response for an incipient polymerisation, including shortstop capability, relief routing and the decision point for evacuation, and train on it before the first delivery.
Hazard Summary
Classification: Skin Corr. 1A (H314), Acute Tox. 4 by oral, dermal and inhalation routes, STOT SE 3 (H335), Flam. Liq. 3, and very toxic to aquatic life with long-lasting effects. Transported as Class 8 corrosive with a Class 3 flammable subsidiary risk.
The freezing point is the distinctive hazard: acrylic acid solidifies at 13 °C, which is reached routinely in transport and unheated storage in most of the world. As it crystallises, MEHQ is excluded from the solid, so the frozen mass is essentially uninhibited while the surrounding liquid holds an excess. Applying a steam lance or a drum heater to one spot creates a pool of hot, uninhibited monomer, which is a documented cause of runaway polymerisation. Thaw slowly, thaw completely, and mix before use.
Corrosive: causes severe skin burns and serious eye damage. Contact requires immediate and prolonged irrigation and medical attention, and the burn may progress after the initial exposure.
Polymerisation: exothermic and self-accelerating once started. Initiators include peroxides, heat, alkali contact, iron contamination and loss of inhibitor. In a closed vessel the consequence is overpressure and rupture.
Inhibitor and oxygen: MEHQ requires dissolved oxygen to function. A pure nitrogen blanket — standard practice on many corrosive liquids — disables it. Confirm this explicitly with whoever will operate the storage.
Dimerisation: acrylic acid slowly converts to diacrylic acid on standing, faster when warm, and the reaction is not reversible. Rising dimer content indicates thermal history and reduces the usable material, which is why it appears on the specification and is worth re-testing on receipt.
PPE minimum: chemical goggles and face shield, corrosive-rated gloves and suit, with respiratory protection where vapour or mist can be generated.
Consult the full SDS and the producer's safe handling guidance for inhibitor management, thawing procedure, exposure limits and emergency response before any use.
Frequently Asked Questions
Technical and commercial questions about Acrylic Acid sourcing and specifications.
What is acrylic acid used for?
The single largest outlet is superabsorbent polymer for disposable hygiene products, made by neutralising the acid to sodium acrylate and crosslinking it. After that come acrylate esters — butyl, ethyl, methyl and 2-ethylhexyl — which go into pressure-sensitive adhesives, paints, textile binders and leather finishes. Polyacrylic acid itself is used as a detergent builder, a scale inhibitor in water treatment, a concrete superplasticiser and a rheology modifier in cosmetics and pharmaceuticals.
Why is a freezing point of 13 °C such a serious issue?
Because of what happens to the inhibitor. Acrylic acid is stabilised with around 200 ppm of MEHQ, and when the acid crystallises the inhibitor is excluded from the crystal lattice and concentrates in whatever liquid remains. The solid is therefore effectively uninhibited. If someone then applies a drum heater or steam lance to one area, they create a local pool of warm, uninhibited monomer — which is exactly the condition needed to start a polymerisation. The correct procedure is to warm the entire container slowly, at no more than 35 °C, until it is fully liquid, then mix it thoroughly so the inhibitor is evenly redistributed before any material is drawn off. Thirteen degrees is reached in ordinary winter conditions across much of the world, so this is not an edge case.
What is the difference between crude and glacial acrylic acid?
Crude or technical acrylic acid is used to make acrylate esters, where the esterification step and the subsequent purification tolerate a higher level of aldehydes, acetic acid and other carbonyl impurities. Glacial acrylic acid is the purified grade required for superabsorbent polymer and for polyacrylic acid, where the acid is polymerised directly and any chain-transfer or colour-forming impurity carries straight into the product. The distinguishing figures are furfural, benzaldehyde, total aldehydes and maleic anhydride, all of which are held to single-digit parts per million in glacial grade.
What does dimer content tell you?
It tells you the thermal history of the material and how much life it has left. Acrylic acid slowly adds to itself to form diacrylic acid, and the reaction runs faster the warmer the material is stored. It is not reversible, so dimer only ever accumulates. A lot arriving with elevated dimer has been held warm or held long somewhere in the chain, and in superabsorbent polymer production the dimer acts as a crosslinker in its own right, which shifts the network properties of the finished product. Testing dimer on receipt is more informative than testing assay.
Why does acrylic acid need oxygen present with its inhibitor?
MEHQ, the monomethyl ether of hydroquinone, does not scavenge radicals on its own — it works through a mechanism that requires dissolved oxygen. Remove the oxygen and the inhibitor stops functioning while still being present on the certificate. This is the same dependency that vinyl acetate and acrylonitrile have, and it means acrylic acid is stored under air or under nitrogen with a deliberately controlled oxygen content. Anyone applying general flammable-liquid practice and blanketing the tank with pure nitrogen will disable the protection without any visible sign that they have done so.
What documentation does Chelora provide?
Every shipment includes a Certificate of Analysis covering purity, MEHQ inhibitor as measured, water, acetic and propionic acid, diacrylic acid dimer, furfural, benzaldehyde, total aldehydes, maleic anhydride, iron, colour and freezing point; a Safety Data Sheet to GHS and REACH format; UN 2218 Class 8 dangerous goods documentation declared as stabilized; an origin certificate; and destination-market or food-contact certificates where the downstream application requires them.
Request a quote or specification sheet
Talk to Chelora's sourcing team about Acrylic Acid grade, volume, logistics, documentation, and lead times. We respond within one business day.
