Methyl ethyl ketone peroxide

Methyl ethyl ketone peroxide (MEKP) is an organic peroxide with the formula [(CH3)(C2H5)C(O2H)]2O2. MEKP is a colorless oily liquid. It is widely used in vulcanization (crosslinking) of polymers.

It is derived from the reaction of methyl ethyl ketone and hydrogen peroxide under acidic conditions. Several products result from this reaction including a cyclic dimer. The linear dimer, the topic of this article, is the most prevalent. and this is the form that is typically quoted in the commercially available material.

Solutions of 30 to 40% MEKP are used in industry and by hobbyists as catalyst to initiate the crosslinking of unsaturated polyester resins used in fiberglass, and casting. For this application, MEKP often is dissolved in a phlegmatizer such as dimethyl phthalate, cyclohexane peroxide, or diallyl phthalate to reduce sensitivity to shock. Benzoyl peroxide can be used for the same purpose.

Safety
Whereas acetone peroxide is a white powder at STP, MEKP is slightly less sensitive to shock and temperature, and more stable in storage.

MEKP is a severe skin irritant and can cause progressive corrosive damage or blindness.

The volatile decomposition products of MEKP can contribute to the formation of vapor-phase explosions. Ensuring safe storage is important, and the maximum storage temperature should be limited to below 30 °C.