Trigonox® HMa is a methyl isobutyl ketone peroxide (MIBKP) formulation for the curing of unsaturated polyester resins as such or in the presence of a cobalt accelerator in the temperature range of 60-150°C. Trigonox® HMa can be used in combination with a cobalt accelerator (e.g. Accelerator NL-49PN) for those applications where a long gel time or production time is required at ambient temperature and a fast cure at higher temperatures e.g. 60-100°C. Application area can be: filament winding and production of flat and corrugated sheets. Trigonox® HMa shows also without the addition of a cobalt accelerator a high reactivity at elevated temperatures, which is demonstrated by its low activation temperature. Trigonox® HMa can therefore successfully be used in the temperature range of approximately 80-150°C: for the production of flat and corrugated sheets where a discoloration by the cobalt accelerator is not acceptable, as kicker for the pultrusion application in combination with a low reactive peroxide like Trigonox® 29-IN50 or Trigonox® C. The low reactive peroxide must be included in the formulation in order to achieve a complete cure.