An electric arc-blast nozzle (5, 20) for a circuit breaker comprising: - a neck-forming median part internally defining an axial electric arc cut-off passage and formed with a first dielectric material obtained from a first composition comprising a fluorocarbon polymer matrix, - first and second end parts (9, 11) also formed with the first dielectric material and extending on either side of the median part which are respectively intended to receive first and second arc contacts (1, 3), the first and second arc contacts (1, 3) being axially moveable in relation to each other, between a circuit breaker opening position in which the first and second arc contacts (1, 3) are separated from each other and a circuit breaker closing position in which the first and second arc contacts (1, 3) are in contact with each other and in which the second arc contact partially closes the axial passage of the median part, an electric arc cut-off gas circulating in the axial passage of the median part to cut an electric arc that is likely to be formed during the movement of the first and second arc contacts (1, 3) from the closing position to the opening position of the circuit breaker, and - a sheath that is only disposed on the external surface of the first end part and on a portion of the external surface of the neck-forming median part, said portion having the same radial external section than the first end part, and that is formed with a second dielectric material being different from the first dielectric material and being obtained from a second composition comprising a polymer, characterized in that the polymer of the second composition is a thermoplastic polymer chosen from either a polysulfone or a polyetherimide and in that the second composition does not comprise fibrous reinforcements. - a neck-forming median part internally defining an axial electric arc cut-off passage and formed with a first dielectric material obtained from a first composition comprising a fluorocarbon polymer matrix, - first and second end parts (9, 11) also formed with the first dielectric material and extending on either side of the median part which are respectively intended to receive first and second arc contacts (1, 3), the first and second arc contacts (1, 3) being axially moveable in relation to each other, between a circuit breaker opening position in which the first and second arc contacts (1, 3) are separated from each other and a circuit breaker closing position in which the first and second arc contacts (1, 3) are in contact with each other and in which the second arc contact partially closes the axial passage of the median part, an electric arc cut-off gas circulating in the axial passage of the median part to cut an electric arc that is likely to be formed during the movement of the first and second arc contacts (1, 3) from the closing position to the opening position of the circuit breaker, and - a sheath that is only disposed on the external surface of the first end part and on a portion of the external surface of the neck-forming median part, said portion having the same radial external section than the first end part, and that is formed with a second dielectric material being different from the first dielectric material and being obtained from a second composition comprising a polymer, characterized in that the polymer of the second composition is a thermoplastic polymer chosen from either a polysulfone or a polyetherimide and in that the second composition does not comprise fibrous reinforcements.