Methyl Ethyl Ketone
Properties
| State | Liquid (colorless with sweet, sharp odor) |
| Color | Colorless |
| Solubility | Soluble in water (275 g/L at 20°C); miscible with ethanol, ether, and most organic solvents |
| Melting Point | -86°C |
| Boiling Point | 80°C |
About Methyl Ethyl Ketone
Methyl ethyl ketone (MEK, 2-butanone) is the second-simplest ketone after acetone, and the workhorse solvent in coatings, adhesives, and degreasing where acetone evaporates a hair too fast. The 80°C boiling point puts MEK's evaporation rate at about 3.7 (n-butyl acetate = 1) versus acetone's 5.6 — that ~30% slower flash-off is the entire reason MEK exists as a commercial product. It dissolves nitrocellulose, vinyl, acrylic, and polyester resins thoroughly enough to give a coating contractor flow and leveling time before the film sets. Global production runs around 1.5 million tonnes a year, mostly via dehydrogenation of 2-butanol over a Cu/Zn catalyst at 400-500°C, with some byproduct from the Wacker oxidation of n-butenes and from cumene hydroperoxide processes. Two specific uses dominate the literature. First, MEK is the precursor to MEK peroxide (MEKP), the methyl ethyl ketone peroxide that fiberglass-boat builders mix into polyester resin at 1-2% to initiate cure — drop in a few cc of MEKP at room temperature and the resin gels in 20-40 minutes. Second, MEK is one of the few solvents that aggressively swells PVC and ABS, which is why plumbing and pipe-cement formulations rely on it to chemically weld plastic joints. The OSHA-listed neuropathy in shoe-factory workers from MEK + n-hexane co-exposure is the textbook example of solvent synergistic toxicity — MEK induces CYP2E1 and accelerates n-hexane bioactivation to 2,5-hexanedione, a powerful neurotoxin.
Where you'll encounter it
If you have ever brushed PVC pipe cement onto a fitting and felt the immediate softening as the joint chemically welded, you used MEK as the active solvent in that purple primer. In a fiberglass boat-repair job — mixing polyester resin from a gallon can with a few squirts of MEKP catalyst and rolling it into the cloth — you are using both MEK and its peroxide derivative back-to-back. The MEK in the laminating resin volatilizes off, the MEKP initiates radical polymerization of the styrene-polyester double bonds, and you have about 25 minutes of working time before exotherm kicks in. In an analytical lab, MEK is the diluent for nitrocellulose-based GC standards and a common rinse solvent in HPLC system flushes. The shoe-factory n-hexane neuropathy story is required reading in occupational health: workers exposed to mixed solvents with both MEK and n-hexane developed peripheral nerve damage at exposure levels where either alone was much less toxic.
Common Uses
- Solvent for nitrocellulose, vinyl, and acrylic lacquers and industrial coatings
- PVC and ABS pipe cement (chemically welds plastic plumbing joints)
- MEK peroxide (MEKP) precursor for polyester and vinyl-ester resin curing in fiberglass
- Dewaxing solvent for lubricating-oil refining (MEK-toluene mix)
- Printing-ink and adhesive solvent; metal-degreasing and paint-stripper formulations
Safety Information
GHS: H225 (highly flammable liquid, flash point -9°C, autoignition 505°C), H319 (causes serious eye irritation), H336 (may cause drowsiness or dizziness). Airborne exposure limits are set on both an 8-hour average and a short-term basis, well below the concentrations that produce narcosis. Vapor density 2.5 (heavier than air — pools in low areas, ignition risk). Acute exposure: eye, nose, throat irritation; CNS depression at high concentrations (headache, dizziness, narcosis at >2000 ppm). Critical interaction: MEK induces CYP2E1, which accelerates n-hexane metabolism to neurotoxic 2,5-hexanedione — the textbook case for solvent synergistic neuropathy in shoe and printing workers. MEK can form explosive peroxides on prolonged storage with air exposure (less prone than diethyl ether but real). Use grounded containers; keep ignition sources away. P95 respirator and nitrile gloves for extended handling.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.