Methyl methacrylate, usually shortened to MMA, is an organic compound registered under CAS number 80-62-6 with the molecular formula C5H8O2. It is the methyl ester of methacrylic acid and appears at room temperature as a colourless liquid with a sharp, fruity odour. The monomer is produced on a large industrial scale because it is the fundamental building block of polymethyl methacrylate, the transparent thermoplastic commonly called acrylic glass.
What Is Another Name for Methyl Methacrylate?
Technical documents and commercial catalogues list several accepted synonyms for the same substance. The most common are methacrylic acid methyl ester, methyl 2-methyl-2-propenoate, methyl 2-methylacrylate, 2-methyl-2-propenoic acid methyl ester, and simply MMA monomer. All of these terms describe one compound with CAS number 80-62-6 and the formula C5H8O2, so checking the CAS number is the most reliable way to confirm identity in a cross-border transaction.
Methyl methacrylate - standard commercial name
Methacrylic acid methyl ester - systematic ester name
Methyl 2-methyl-2-propenoate - alternative systematic name
Methyl 2-methylacrylate - short systematic form
MMA / MMA monomer - abbreviation used on specifications and tank labels
MMA should not be confused with methacrylic acid, which has CAS number 79-41-4. The two compounds differ in corrosivity, acidity, and handling requirements, and they are not interchangeable even though one is the feedstock for the other.
Properties and Quality Specifications
| Property | Typical value |
|---|---|
| CAS number | 80-62-6 |
| Molecular formula | C5H8O2 |
| Molecular weight | about 100.12 g/mol |
| Appearance | Colourless liquid, sharp fruity odour |
| Density | about 0.94 g/cm³ at 20 °C |
| Boiling point | about 100 to 101 °C at atmospheric pressure |
| Freezing point | about minus 48 °C |
| Flash point | about 10 °C, flammable liquid |
| Water solubility | Slightly soluble |
Commercial grades are supplied against a tight specification. A purity of at least 99.5 percent, water content below 0.1 percent, and colour below 5 on the platinum-cobalt scale are typical acceptance limits, and a low acid content expressed as methacrylic acid is normally specified as well. Because the molecule carries a reactive carbon-carbon double bond, it polymerises readily, so the certificate of analysis must always be read together with the inhibitor figure rather than in isolation.
Why the Monomer Needs an Inhibitor
The reactive double bond that makes MMA valuable also makes it unstable in storage. Warm conditions, light exposure, or contact with certain metals can start spontaneous polymerisation, thickening the liquid and eventually setting it solid inside the container. To prevent this, commercial MMA contains a small amount of polymerisation inhibitor, typically in the range of 5 to 25 parts per million.
Inhibitors work only in the presence of dissolved oxygen, which means headspace air matters. Storage tanks and drums should not be purged with nitrogen, and bulk stock should be rotated so that material does not sit undisturbed for long periods. Where an inhibitor is stripped or consumed, the batch must be re-stabilised before use, and any batch showing increased viscosity or haze should be quarantined rather than blended into production.
Main Industrial Uses of MMA
The dominant outlet is polymerisation into polymethyl methacrylate, a transparent, lightweight thermoplastic used for organic glass sheets, optical lenses, light guides, signage, and display panels. Cast sheet and extruded sheet routes both start from the same monomer, with the choice of process determining molecular weight and optical clarity.
Copolymers - reaction with other vinyl monomers produces resins tuned for flexibility, impact resistance, and weatherability
Coatings - acrylic and methacrylic binders for architectural, automotive, and industrial finishes
Adhesives and sealants - structural bonding systems and anaerobic products
Lubricating oil additives - viscosity index improvers and pour point depressants
Ion exchange resins - methacrylate-based beads for water treatment
Medical and dental materials - bone cement, denture bases, and laboratory ware
Textile and leather auxiliaries - binders, finishing agents, and processing aids
Insulation casting compounds - electrical and electronic encapsulation
Because the polymer is colourless and resistant to yellowing, PMMA also competes with glass in lighting diffusers, vehicle light covers, and outdoor signage, where impact resistance and low weight matter more than scratch performance.
Packaging, Storage and Buyer Checks
High-purity MMA moves in steel drums and ISO tanks. Because the monomer is flammable and polymerisable, containers must be kept tightly closed, protected from light and elevated temperature, and stored away from ignition sources and strong oxidising agents. Storage areas should be ventilated and fitted with grounding provisions, and transfer equipment must be bonded so that static cannot build up.
Before shipment, buyers should verify the certificate of analysis for purity, water content, acid content, colour, and inhibitor level, and confirm that the inhibitor was measured on the actual batch. Incoming inspection usually repeats the water and inhibitor checks, since a warm or badly sealed container can lose inhibitor strength during transit. Packaging marks should carry the CAS number 80-62-6 and the correct UN number so that carriers apply the right segregation rules.
Frequently Asked Questions
Q: What is another name for methyl methacrylate?
The common alternatives are methacrylic acid methyl ester, methyl 2-methyl-2-propenoate, methyl 2-methylacrylate, and MMA monomer. All refer to CAS 80-62-6.
Q: Is methyl methacrylate the same as methacrylic acid?
No. MMA is the methyl ester of methacrylic acid. Methacrylic acid carries CAS 79-41-4, while MMA carries CAS 80-62-6, and their properties and uses differ.
Q: Is MMA flammable?
Yes. MMA is a flammable liquid with a flash point of about 10 °C, so it must be kept away from open flames and handled with grounding in well-ventilated areas.
Q: Why does MMA contain an inhibitor?
Its reactive carbon-carbon double bond makes the monomer prone to spontaneous polymerisation, especially when warm, so a small amount of inhibitor keeps it stable during storage and transport.
Q: What is PMMA?
PMMA is polymethyl methacrylate, the polymer formed by polymerising MMA. It is a transparent, lightweight thermoplastic used in organic glass, lenses, and display products.
Q: What is the purity of commercial MMA?
Standard industrial grades are supplied at a purity of at least 99.5 percent, with water content below 0.1 percent and colour below 5 on the platinum-cobalt scale.