CUROX® CM-75R is a liquid mixture of methyl ethyl ketone peroxide and tert-butyl peroxide.It is a red liquid consisting primarily of a mixture of methyl ethyl ketone peroxide and tert-butyl peroxide, which is essentially de-sensitized using phthalate plasticizers.This mixture is used as a curing agent (radical source) for unsaturated polyester resins (particularly vinyl ester resins).Major applications include vacuum impregnation and bag-molding technology, as well as the curing of hand-laid or spray-up reinforced parts at room temperature using cobalt or cobalt/amine accelerators, primarily for thicker laminates. Technical data includes:

Appearance: Red liquid
Active oxygen content: approx. 8.8% (mass fraction)
Hydrogen peroxide content: approx. 0.7% (by mass)
Water content: approx. 1.2% (by mass)
Desensitizer: Dimethyl phthalate
Density (20°C): approximately 1.1 g/cm³
Viscosity (20°C): approximately 19 mPa·s
Miscibility: Miscible with alcohols and phthalates
Critical Temperature (SADT): Above 60°C
Freezer stability: Below -20°C
Recommended storage temperature: 0°C to 30°C
Pot life at 30°C: 6 months from the date of manufacture

Applications include: As a curing agent for all types of UP resins, used in combination with cobalt/cobaltamine accelerators at room temperature. Recommended dosage levels: 1–2.5% as supplied; 0.5–2% when used with a 1% cobalt solution.Suitability for vinyl ester resins is limited. In vinyl ester resins, the cobalt octoate/dimethylaniline combination can accelerate the reaction more effectively. For extended vacuum impregnation/injection, it is sufficient to achieve the gel time for the resin + peroxide + accelerator system. Curing performance depends on the resin type; heat evolution is minimal, and good curing rates are guaranteed across all applications (thin/thick layers). Compared to standard MEKP (Curox M-303), gel time and gel-to-peak time are significantly longer in unsaturated polyester resins.Temperatures below 20°C significantly prolong curing times; therefore, cobalt/amine accelerators should be used. Processing methods include hand lay-up, spraying, fiber winding, and impregnation processes, particularly RTM. When using spraying equipment, follow the manufacturer’s instructions. Ensure that all safety devices are functioning properly, and do not spray peroxides into the air. Additionally, further information on suitable curing agents for unsaturated polyester resins is available in the relevant application manuals. The standard packaging size is a 25-kilogram polyethylene bottle. For detailed information and intended uses, we recommend that you carefully review and test the product according to your specific needs.

United Initiators CUROX®CM-75R Methyl ethyl ketone peroxide 1338-23-4

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