Abstract: An extrusion die is disclosed. The extrusion die can include a body member defining a passage therein, and the passage configured to receive heated material at an ingress end of the body member. A mandrel can be disposed within the passage and configured to divert the heated material around the mandrel within the passage as the heated material traverses the passage from the ingress end to an egress end of the body member. The mandrel can define an interior hollow portion that is configured to receive coolant.

Abstract: An extruder screw (10) for a screw extruder (1) is disclosed having a central shaft (18) and a number of screw flights (20) arranged upon the central shaft (18). At least one of the screw flights (20) includes at least one discontinuity (38) which is an interruption in the screw flight (20) by which a portion of said screw flight (38) is offset circumferentially from the remainder of the screw flight (38). Also disclosed is a screw extruder (1) including a screw (10) having at least one discontinuity (38), a method of cooling material in a screw extruder (1), and a method of extruding material from a screw extruder (1) while cooling material within the screw extruder (1).

Abstract: Compositions which exhibit PTC behavior with a switching temperature (T.sub.s) above 0.degree. C., which have a resistivity at a temperature below T.sub.s of less than 7 ohm. cm, and which comprise a crystalline polymer and a particulate filler component which comprises carbon black having a particle size, D, which is from 20 to 150 millimicrons and a surface area S in m.sup.2 /gram such that S/D is not more than 10. The composition preferably has a peak resistivity of at least 1000 ohm. cm and is electrically stable when aged at elevated temperature. The quantity ##EQU1## is preferably less than 1, especially less than 0.5. Shaped articles of such compositions are prepared by a process in which the carbon black is dispersed in the molten polymer and the dispersion is then melt-shaped, the total energy used in preparing and melt-shaping the dispersion being 1 to 300 hp. hr. ft.sup.-3, preferably 1 to 100 hp. hr. ft.sup.-3, especially 1 to 50 hp. hr. ft.sup.-3.