A heat curable powder coating composition comprising: i) at least one crystalline polyester resin having a melting enthalpy of at least 40 J/ g and a melting temperature, present in an amount of at most 90 wt%; and ii) at least one amorphous polyester resin having a melting enthalpy lower than 40 J/ g; and iii) at least one crosslinking agent; and iv) at least one thermal radical initiator, wherein, - the at least one crystalline polyester resin and/or the at least one amorphous polyester resin has di-acid ethylenic unsaturations; - the at least one crosslinking agent is either crystalline having a melting enthalpy of at least 40 J/g and a melting temperature, or amorphous having a melting enthalpy lower than 40 J/ g; - the at least one crosslinking agent has reactive unsaturations that are reactable with the ethylenic unsaturations of the di-acid ethylenic unsaturations of the at least one crystalline polyester resin and/ or the at least one amorphous polyester resin to be crosslinked, said unsaturations of the crosslinking agent are different from the unsaturations of the at least one crystalline polyester resin and the unsaturations of the at least one amorphous polyester resin; - the wt% is based on the total amount of i)+ ii)+ iii); - the melting enthalpy of the at least one crystalline polyester resin, the melting enthalpy of the at least one amorphous polyester resin, the melting enthalpy of the crosslinking agent, the melting temperature of the at least one crystalline polyester resin and the melting temperature of the at least one crosslinking agent when the crosslinking agent is crystalline, are each measured via Differential Scanning Calorimetry according to the description. i) at least one crystalline polyester resin having a melting enthalpy of at least 40 J/ g and a melting temperature, present in an amount of at most 90 wt%; and ii) at least one amorphous polyester resin having a melting enthalpy lower than 40 J/ g; and iii) at least one crosslinking agent; and iv) at least one thermal radical initiator, wherein, - the at least one crystalline polyester resin and/or the at least one amorphous polyester resin has di-acid ethylenic unsaturations; - the at least one crosslinking agent is either crystalline having a melting enthalpy of at least 40 J/g and a melting temperature, or amorphous having a melting enthalpy lower than 40 J/ g; - the at least one crosslinking agent has reactive unsaturations that are reactable with the ethylenic unsaturations of the di-acid ethylenic unsaturations of the at least one crystalline polyester resin and/ or the at least one amorphous polyester resin to be crosslinked, said unsaturations of the crosslinking agent are different from the unsaturations of the at least one crystalline polyester resin and the unsaturations of the at least one amorphous polyester resin; - the wt% is based on the total amount of i)+ ii)+ iii); - the melting enthalpy of the at least one crystalline polyester resin, the melting enthalpy of the at least one amorphous polyester resin, the melting enthalpy of the crosslinking agent, the melting temperature of the at least one crystalline polyester resin and the melting temperature of the at least one crosslinking agent when the crosslinking agent is crystalline, are each measured via Differential Scanning Calorimetry according to the description. - the at least one crystalline polyester resin and/or the at least one amorphous polyester resin has di-acid ethylenic unsaturations; - the at least one crosslinking agent is either crystalline having a melting enthalpy of at least 40 J/g and a melting temperature, or amorphous having a melting enthalpy lower than 40 J/ g; - the at least one crosslinking agent has reactive unsaturations that are reactable with the ethylenic unsaturations of the di-acid ethylenic unsaturations of the at least one crystalline polyester resin and/ or the at least one amorphous polyester resin to be crosslinked, said unsaturations of the crosslinking agent are different from the unsaturations of the at least one crystalline polyester resin and the unsaturations of the at least one amorphous polyester resin; - the wt% is based on the total amount of i)+ ii)+ iii); - the melting enthalpy of the at least one crystalline polyester resin, the melting enthalpy of the at least one amorphous polyester resin, the melting enthalpy of the crosslinking agent, the melting temperature of the at least one crystalline polyester resin and the melting temperature of the at least one crosslinking agent when the crosslinking agent is crystalline, are each measured via Differential Scanning Calorimetry according to the description.