What is MEK (Methyl Ethyl Ketone)?
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What is MEK (Methyl Ethyl Ketone)? The Complete Industrial Solvent Guide
Methyl Ethyl Ketone (MEK), also known as 2-butanone, is one of the most widely used industrial solvents in the world. From automotive coatings to aerospace adhesives, MEK delivers fast evaporation, exceptional solvency, and reliable performance across dozens of industries. This guide covers everything you need to know—properties, applications, safety, comparisons, and sourcing.
Chemical Properties of MEK
Methyl Ethyl Ketone (C₄H₈O) is a colorless liquid with a sharp, sweet odor. It belongs to the ketone family and is structurally similar to acetone, but with a slightly higher boiling point and slower evaporation rate—making it preferable for many coating and adhesive applications where you need more working time.
| Property | Value |
|---|---|
| Chemical Formula | C4H8O (CH3COCH2CH3) |
| IUPAC Name | Butan-2-one |
| Molecular Weight | 72.11 g/mol |
| Boiling Point | 79.6°C (175.3°F) |
| Flash Point | -9°C (15.8°F) |
| Density | 0.805 g/cm³ at 20°C |
| Water Solubility | 29.3 g/100 mL at 20°C |
| Vapor Pressure | 78 mmHg at 20°C |
| Evaporation Rate | 3.8 (butyl acetate = 1) |
| Appearance | Colorless, clear liquid |
| Odor | Sharp, sweet, acetone-like |
MEK is miscible with most organic solvents and partially soluble in water. Its fast evaporation rate (3.8x butyl acetate) and strong dissolving power for resins, polymers, and adhesives make it indispensable in industrial settings. For a deeper understanding of solvent chemistry, see our Ultimate Guide to Industrial Solvents.
Industrial Applications of MEK
MEK’s combination of fast evaporation, strong solvency, and compatibility with numerous resins makes it one of the most versatile solvents available. Here are its primary applications:
Paints & Coatings
MEK dissolves nitrocellulose, acrylic, vinyl, and alkyd resins used in automotive finishes, industrial coatings, and wood lacquers. Its evaporation rate produces smooth, uniform films. Learn more in our paint thinning guide.
Adhesives & Sealants
Critical in formulating contact cements, PVC pipe cements, and structural adhesives. MEK’s solvency enables strong polymer bonding—even for bonding LEGO bricks permanently.
Degreasing & Cleaning
Removes oils, greases, waxes, and manufacturing residues from metal and plastic surfaces. MEK evaporates cleanly without residue, making it ideal for pre-painting surface prep.
Printing Inks
Used in flexographic and gravure inks for packaging and labels. MEK dissolves a wide range of ink resins and evaporates at the right speed for high-speed printing operations.
3D Printing
MEK smooths and welds ABS and ASA 3D prints through solvent vapor polishing, producing glossy professional finishes. See our MEK for 3D Print Finishing guide.
Polymer Manufacturing
Used as a process solvent in polymer composite fabrication, resin synthesis, and plastic welding. Our Engineer’s Masterclass on MEK dives deep into polymer applications.
MEK vs. Other Solvents: Comparison Table
Choosing the right solvent depends on evaporation rate, solvency strength, toxicity profile, and cost. Here’s how MEK stacks up against common alternatives. For a comprehensive selection guide, read Choosing the Right Solvent for Industrial Cleaning.
| Solvent | Boiling Pt | Evap Rate | Solvency | Toxicity | Best For |
|---|---|---|---|---|---|
| MEK | 79.6°C | 3.8 | High | Moderate | Coatings, adhesives, degreasing |
| Acetone | 56.0°C | 5.6 | High | Low | Quick cleaning, nail polish removal |
| Toluene | 110.6°C | 2.0 | Very High | Higher | Paint thinning, rubber dissolving |
| IPA 99% | 82.6°C | 2.3 | Moderate | Low | Electronics cleaning, disinfection |
| Ethyl Acetate | 77.1°C | 4.1 | Moderate | Low | Inks, mild adhesive work |
| n-Butyl Acetate | 126°C | 1.0 | Moderate | Low | Automotive clear coats, slow-dry finishes |
| Cyclohexanone | 155.6°C | 0.3 | Very High | Moderate | PVC welding, specialty coatings |
Why Choose MEK Over Acetone?
While acetone and MEK are both ketone solvents, they serve different niches:
- Slower evaporation: MEK evaporates ~30% slower than acetone, giving better film formation in paints and coatings
- Higher boiling point: 79.6°C vs. 56°C means less product loss during application
- Better resin compatibility: MEK dissolves certain vinyl and epoxy resins that acetone struggles with
- Stronger bonding: In adhesive applications, MEK creates stronger solvent welds in plastics like ABS and PVC
- Wider formulation range: MEK blends more smoothly with high-boiling solvents for custom evaporation profiles
For quick cleaning tasks and situations where low toxicity is paramount, acetone remains the better choice. For anything requiring controlled evaporation and strong resin solvency, MEK wins. See our ACS Grade Acetone Guide for purity-critical applications.
Industry-Specific Use Cases
| Industry | Application | Why MEK |
|---|---|---|
| Automotive | Basecoat/clearcoat systems, prep solvent | Fast flash-off, excellent resin compatibility |
| Aerospace | Composite layup, adhesive bonding | Controlled evaporation, high solvency for epoxies |
| Electronics | PCB defluxing, conformal coating removal | Residue-free cleaning, PCB solvent compatibility |
| Packaging | Flexographic/gravure ink systems | Right evaporation for press speed, good resin range |
| Furniture | Lacquer thinning, surface prep, staining | Smooth finish, fast dry, compatible with nitrocellulose |
| Marine | Fiberglass preparation, gelcoat thinning | Dissolves polyester resins, evaporates before cure |
Safety and Handling
Personal Protective Equipment (PPE)
| Hazard | Protection Required | Specification |
|---|---|---|
| Eye contact | Chemical splash goggles | ANSI Z87.1 rated |
| Skin contact | Chemical-resistant gloves | Nitrile or butyl rubber, 8+ mil thickness |
| Inhalation | Respiratory protection | OV cartridge respirator (NIOSH-approved) when above PEL |
| Fire risk | No ignition sources | Grounded/bonded containers, explosion-proof equipment |
Exposure Limits
- OSHA PEL: 200 ppm (590 mg/m³) TWA
- ACGIH TLV: 200 ppm TWA, 300 ppm STEL
- NIOSH REL: 200 ppm TWA, 300 ppm STEL
Storage Requirements
Store MEK in a cool, dry, well-ventilated area away from heat sources, sparks, and open flames. Use approved flammable liquid storage cabinets (NFPA 30 compliant). Keep containers tightly sealed and grounded during dispensing. For comprehensive guidance, see our Safe Storage Tips for Solvents.
Sourcing Quality MEK
Not all MEK is created equal. Industrial-grade MEK may contain water, methanol, or other impurities that affect performance. For critical applications like analytical chemistry, electronics cleaning, or pharmaceutical processing, understanding chemical grades matters.
Alliance Chemical offers high-purity MEK in multiple grades and package sizes:
- MEK (Standard Grade) — ideal for general-purpose degreasing, coatings, and adhesives
- MEK ACS Grade — certified for analytical and laboratory applications
Ready to Order MEK?
Alliance Chemical supplies high-purity MEK in quart, gallon, 5-gallon, and drum quantities. Fast shipping, competitive pricing, and technical support from our team.
Shop MEK Now | Browse All Ketones | Full Solvents Collection
Frequently Asked Questions
What is MEK used for?
MEK is used as a solvent in paints, coatings, adhesives, printing inks, and degreasing operations. It’s also used in 3D print finishing, PVC pipe cementing, and polymer composite manufacturing.
Is MEK the same as acetone?
No. Both are ketone solvents, but MEK (C₄H₈O) has a higher boiling point (79.6°C vs. 56°C), slower evaporation rate, and dissolves some resins that acetone cannot. MEK is preferred for coatings and adhesives; acetone is better for quick cleaning.
Is MEK toxic?
MEK has moderate toxicity. At normal occupational exposure levels (below 200 ppm), it’s considered safe with proper ventilation and PPE. It’s less toxic than toluene, xylene, or TCE. The body metabolizes MEK naturally, and it doesn’t bioaccumulate.
Can MEK be used on plastic?
Yes, but carefully. MEK dissolves ABS, PVC, polycarbonate, and acrylic—which is useful for solvent welding but destructive if you want to preserve the surface. It’s safe on polyethylene (PE) and polypropylene (PP), which resist most solvents.
What’s replacing MEK in industry?
Some operations are switching to d-limonene, acetone, or acetate esters for environmental reasons. However, MEK remains irreplaceable in many applications due to its unique combination of evaporation rate and solvency power.
Frequently Asked Questions
What is MEK (methyl ethyl ketone) and what is it used for?
MEK (2-butanone, C₄H₈O) is a fast-evaporating ketone solvent used in coatings and paint manufacturing, adhesive formulations, plastic welding (ABS, PVC, polycarbonate), vinyl and synthetic leather production, printing inks, and industrial cleaning. It provides a balance of solvency power, evaporation rate, and cost that makes it essential in many manufacturing processes.
How does MEK compare to acetone as a solvent?
MEK is a stronger solvent for many resins and coatings, with better wetting properties and a more controlled evaporation rate (3.8 vs acetone 5.6). Acetone has a higher OSHA PEL (1,000 vs 200 ppm), making it safer for workers. MEK produces smoother coating finishes; acetone is better for fast cleaning. For plastic welding, MEK provides stronger bonds.
What safety precautions are needed when working with MEK?
MEK has an OSHA PEL of 200 ppm TWA—use in well-ventilated areas or with an organic vapor respirator. Flash point is 16°F (-9°C), making it extremely flammable—eliminate all ignition sources. Wear nitrile gloves (not latex) and safety glasses. MEK is a CNS depressant at high concentrations—symptoms include headache, dizziness, and nausea.
Can MEK be used to weld or bond plastics?
Yes, MEK is widely used for solvent welding of ABS, PVC, acrylic, and polycarbonate plastics. It partially dissolves the surfaces, which fuse together as the solvent evaporates, creating a bond stronger than adhesive joints. Apply a thin layer to both surfaces, press together immediately, and allow 24 hours for full cure. MEK does not work on polyethylene or polypropylene.
