Methyl ethyl ketone peroxide

Methyl ethyl ketone peroxide (CAS 1338-23-4), commonly known as MEKP, is an organic peroxide used as a free-radical initiator in polymer curing and crosslinking systems. Supplied as a solution rather than in pure form, it activates resin systems at room temperature without requiring elevated heat. Formulators and compounders rely on it to control cure speed and crosslink density across a range of thermoset applications. MEKP is the standard initiator for curing unsaturated polyester and vinyl ester resins in fiberglass-reinforced composites.

This includes marine hulls, automotive panels, and construction laminates. In combination with cobalt-based accelerators, it enables ambient-temperature cure cycles that are critical for open-mold and hand lay-up fabrication. Rubber compounders use it as a crosslinking agent to improve heat resistance and mechanical performance in elastomeric profiles and molded parts. It also initiates polymerization in gel coats and casting resins.

In these applications, cure uniformity directly affects surface quality and product yield. MEKP is supplied as a liquid solution, typically diluted in plasticizers or inert carriers to reduce reactivity hazards during handling and transport. Standard commercial concentrations range from approximately 33% to 60% active oxygen content, with grades varying by reactivity profile to suit different resin systems and processing conditions.

Technical-grade material is the norm for most industrial uses. Buyers should confirm active oxygen percentage and dilution carrier with suppliers when qualifying for specific applications to ensure compatibility.