Abstract: An inverted cone is disposed in a housing having a complementarily-shaped conical portion into which the cone is introduced. Means are provided for introducing thermoset plastic material to be heated, into the housing at the base end of the cone so that the material flows through the region defined between the cone and the housing. Means are provided for heating the region between the cone and the housing and for removing the heated plastic material from near the tip of the cone. There is also preferably provided a mixing chamber near the tip of the cone to ensure uniform thermal and mechanical mixture of the plastic material. The present invention provides uniform heating of the material being processed.