- CUROX® M-503 is a colorless liquid consisting of methyl ethyl ketone-based peroxides that have been desensitized with phthalate plasticizers.
- It is used as a free-radical source for initiating unsaturated polyester resins.
- Main Applications: Hand lay-up, spray-up, continuous lamination, centrifugal casting, fiber winding, and polyester concrete.
- Appearance: Colorless liquid
- Active oxygen content: approx. 9.5% w/w
- Free hydrogen peroxide content: approx. 3.5% w/w
- Water content: approx. 5.0% w/w
- Desensitizer: Dimethyl phthalate
- Density at 20°C: approx. 1.12 g/cm³
- Viscosity at 20°C: approx. 20 mPa·s
- Solubility: Miscible with alcohols and phthalates
- Primarily used in conjunction with cobalt catalysts at room temperature to cure all types of unsaturated polyester resins.
- Standard dosage levels: 1–3% as supplied; 0.5–2% when used with a 1% cobalt solution.
- Compared to standard MEKP, the “pot life” (gel time of resin + peroxide + catalyst) is shorter, but can be extended by adding Inhibitor TC-510.
- High heat generation rate. Relatively short demolding time. Curing time is significantly prolonged at temperatures below 20°C; in such cases, a cobalt/amine catalyst should be used.