Aqueous emulsion composition comprising: - one or more organic peroxides of formula (I): in which formula (I) R 1 and R 2 , which may be identical or different, represent a linear, branched or cyclic C 1 -C 20 alkyl group which may comprise, and is preferably interrupted with, one or more heteroatoms, preferably one or more oxygen atoms; - one or more organic peroxides of formula (II): in which formula (II) R 3 and R 4 , which may be identical or different, represent a linear, branched or cyclic C 1 -C 20 alkyl group which may comprise, and is preferably interrupted with, one or more heteroatoms, preferably one or more oxygen atoms, and/or is optionally substituted with one or more hydroxyl groups, said organic peroxide of formula (II) being a hydroxyperoxyester or at least one of said organic peroxides of formula (II) being a hydroxyperoxyester; the organic peroxide(s) of formula (I) and the organic peroxide(s) of formula (II) being present in a concentration ranging from 40% to 70% by weight relative to the total weight of the composition, preferably ranging from 40% to 65% by weight relative to the total weight of the composition, more preferentially ranging from 40% to 60% by weight relative to the total weight of the composition. - one or more organic peroxides of formula (I): in which formula (I) R 1 and R 2 , which may be identical or different, represent a linear, branched or cyclic C 1 -C 20 alkyl group which may comprise, and is preferably interrupted with, one or more heteroatoms, preferably one or more oxygen atoms; - one or more organic peroxides of formula (II): in which formula (II) R 3 and R 4 , which may be identical or different, represent a linear, branched or cyclic C 1 -C 20 alkyl group which may comprise, and is preferably interrupted with, one or more heteroatoms, preferably one or more oxygen atoms, and/or is optionally substituted with one or more hydroxyl groups, said organic peroxide of formula (II) being a hydroxyperoxyester or at least one of said organic peroxides of formula (II) being a hydroxyperoxyester; the organic peroxide(s) of formula (I) and the organic peroxide(s) of formula (II) being present in a concentration ranging from 40% to 70% by weight relative to the total weight of the composition, preferably ranging from 40% to 65% by weight relative to the total weight of the composition, more preferentially ranging from 40% to 60% by weight relative to the total weight of the composition. in which formula (II) R 3 and R 4 , which may be identical or different, represent a linear, branched or cyclic C 1 -C 20 alkyl group which may comprise, and is preferably interrupted with, one or more heteroatoms, preferably one or more oxygen atoms, and/or is optionally substituted with one or more hydroxyl groups, said organic peroxide of formula (II) being a hydroxyperoxyester or at least one of said organic peroxides of formula (II) being a hydroxyperoxyester; the organic peroxide(s) of formula (I) and the organic peroxide(s) of formula (II) being present in a concentration ranging from 40% to 70% by weight relative to the total weight of the composition, preferably ranging from 40% to 65% by weight relative to the total weight of the composition, more preferentially ranging from 40% to 60% by weight relative to the total weight of the composition. <EOS>