Heat-curable powder coating composition

A one component heat curable powder coating composition comprising:

• (i) a polyester resin containing reactive unsaturations, the polyester resin having a weight per the reactive unsaturations (WPU) as determined using 1H-NMR which is higher than 250 and lower than 1500 g/mole,
• (ii) a thermal initiation system comprising a peroxide chosen from the group consisting of compounds represented by formula (1)
• wherein
• R1 and R2 each independently stand for an optionally substituted alkyl of 1 to 30 C-atoms, wherein the 1 to 30 C-atoms do not include the C-atoms of the substituents or for an optionally substituted aryl of 6 to 18 C-atoms, and wherein the 6 to 18 C-atoms do not include the C-atoms of the substituents, and
• (iii) a co-crosslinker having a weight per unsaturation (WPU) as determined using 1H-NMR higher than 150 and lower than 870 g/mole, said crosslinker being chosen from the group consisting of vinylethers, vinyletherurethanes, vinylesters, vinylamides, itaconates, enamines, vinylureas and mixtures thereof, wherein
• all of the reactive unsaturations are carbon-carbon double bonds connected directly to an electron withdrawing group and are reactive towards radicals generated by the peroxide, and wherein
• the thermal initiation system is present in an amount such that when the powder coating composition is applied to a substrate and cured at a temperature of 130° C. for 20 minutes, the resulting coating resists at least 50 acetone double rubs (ADR), wherein each ADR is a back and forward movement over a surface of the coating having a thickness of approximately 60 μm using a cotton cloth drenched in acetone covering a hammer head having a weight of 980 grams and a contact surface area with the coating of 2 cm2.