Acrylic acid, also known as 2-propenoic acid or vinylformic acid, is the simplest unsaturated carboxylic acid, with the CAS number 79-10-7 and the molecular formula C3H4O2. It is a colourless liquid with a pungent, acrid odour. As a vinyl monomer with a very fast polymerisation rate, it is an essential raw material for acrylate esters and acrylic polymers. Commercial acrylic acid is typically supplied at a purity of 99.5 percent or higher and contains a polymerisation inhibitor that prevents premature reaction during storage and transport.
This article reviews the key properties of acrylic acid, the acrylate esters and polymer building blocks derived from it, its main industrial applications, and the safety and storage practices required for a corrosive, readily polymerisable monomer.
Key Properties of Acrylic Acid
Acrylic acid is miscible with water and with most organic solvents. Dilution with water is exothermic, but it does not react violently with water. The material is a strongly irritating and corrosive organic acid, and it is volatile, evaporating at room temperature into a colourless vapour with a pungent odour.
| Property | Value |
| CAS number | 79-10-7 |
| Molecular formula | C3H4O2 |
| Chemical name | 2-propenoic acid |
| Typical commercial purity | 99.5% or higher |
| Appearance | Colourless liquid, pungent odour |
| Solubility | Miscible with water and most organic solvents |
| Stabilisation | Supplied with a polymerisation inhibitor |
The most important chemical property of acrylic acid is its tendency to polymerise, either alone to form polyacrylic acid or with other monomers to form copolymers. Because polymerisation is highly exothermic and can become hazardous if it runs away, commercial grades are inhibited and must be stored with proper temperature control and ventilation.
Acrylate Esters and Polymer Building Blocks
Most acrylic acid is converted into acrylate esters such as methyl acrylate, ethyl acrylate, butyl acrylate and hydroxyethyl acrylate. Acrylic acid and its acrylates can be homopolymerised or copolymerised with other monomers, including acrylonitrile, styrene, butadiene, vinyl chloride and maleic anhydride. The resulting polymers serve synthetic resins, adhesives, synthetic rubber, synthetic fibres, superabsorbent resins, pharmaceuticals, leather, textiles, chemical fibres, building materials, water treatment, oil exploration and coatings.
Main Industrial Applications
Superabsorbent polymers: the largest single use of acrylic acid is the production of cross-linked polyacrylates that absorb and retain large amounts of water for baby diapers, adult incontinence products, sanitary pads and agricultural water retention.
Adhesives and coatings: acrylate polymers and copolymers form pressure-sensitive adhesives, acrylic emulsion paints, architectural coatings and industrial coatings. Acrylic latexes offer good colour retention, resistance to yellowing and excellent printing performance, and are used as art paper coatings that do not stick to rollers.
Water treatment and polymer additives: polyacrylic acid and its copolymers act as scale inhibitors and dispersants in water treatment systems, and acrylic acid derivatives serve as thickening agents, aggregating agents, softening agents and general polymer additives.
Textiles, leather and oil exploration: acrylic acid based polymers are used in textile finishing, leather processing and chemical fibres, while acrylate copolymers act as drilling fluid additives and components of enhanced oil recovery formulations.
Safety, Storage and Handling of Acrylic Acid
Acrylic acid is corrosive and can cause severe burns to the skin, eyes and respiratory tract. It is volatile and strongly irritating, so handle it only with adequate ventilation, chemical-resistant gloves, protective clothing and eye protection. Because the monomer polymerises exothermically, storage areas must be temperature controlled, the product must be used within its shelf life, and it must never be mixed inadvertently with polymerisation initiators or peroxides. In the event of a spill, contain the liquid, apply suitable neutralising and absorbing media, and dispose of the waste according to local regulations. Always consult the current safety data sheet before handling acrylic acid.
Frequently Asked Questions
Q: What is acrylic acid used for?
Acrylic acid is mainly used to produce acrylate esters and polymers for superabsorbent materials, adhesives, coatings, water treatment chemicals, textiles and oilfield products.
Q: Does acrylic acid react violently with water?
No. Acrylic acid is miscible with water and dilution is exothermic but not a violent reaction. Its main hazard is rapid exothermic polymerisation, which is controlled by inhibitors and temperature management.
Q: What is the CAS number and formula of acrylic acid?
The CAS number is 79-10-7 and the molecular formula is C3H4O2.
Q: What is the largest application of acrylic acid?
The largest application is the production of superabsorbent polymers used in diapers and hygiene products, followed by acrylate esters for adhesives and coatings.
Q: Why is acrylic acid supplied with an inhibitor?
Acrylic acid polymerises readily and exothermically, so a polymerisation inhibitor is added to commercial grades to keep the monomer stable during storage and transport.
Q: Is acrylic acid hazardous?
Yes, acrylic acid is corrosive and irritating to skin, eyes and the respiratory tract. It must be handled with personal protective equipment, ventilation and temperature-controlled storage, following the safety data sheet.