Methyl ethyl ketone (butanone)
A strong, fast ketone solvent and the namesake of the “MEK rub” test used to check whether coatings have cured.
Methyl ethyl ketone (butanone) is a ketone that boils at about 79.6 °C and evaporates quickly (about 3.8 relative to n-butyl acetate). It is highly flammable, with a flash point below 0 °C.
MEK is used in vinyl, acrylic and nitrocellulose lacquers, adhesives, cleanup of epoxy and urethane equipment, and in laboratory and field cure checks. Solvent rubs with MEK are a common way to judge cure under ASTM D5402, and MEK is specified for inorganic zinc primers under ASTM D4752.
MEK is a powerful active solvent for many resins. Cured, crosslinked thermosets resist it, while under-cured or thermoplastic films soften, which is why it works as a cure indicator.
Highly flammable and an eye and respiratory irritant; vapors can cause drowsiness. Ventilate, ground containers and wear solvent-resistant gloves.
How well a coating resists a strong solvent, which indicates whether a reactive coating has crosslinked as intended. Compare results only with the manufacturer’s stated expectations.
No. Unlike acetone, MEK counts as a VOC under US EPA rules.
