Apparatus for continuously foaming a polyimide powder

An apparatus for continuously foaming prepolymer powders, including prepolymer powders that are not susceptible to heating by microwave energy, to form a foam product comprising:

• an oven means for heating a prepolymer powder layer on a conveyor by convection and infrared radiation heating to cause the prepolymer powder to react, foam and form a continuous foam bun;
• a continuous, driven metallic conveyor belt for moving the prepolymer powder through the oven means;
• means for depositing the prepolymer powder on and across the width of the conveyor belt in a layer before the conveyor belt enters the oven;
• means for heating the conveyor belt to between 175.degree. C. and 290.degree. C. prior to depositing the prepolymer powder layer in the conveyor belt to cause the prepolymer powder in contact with and adjacent the conveyor belt to be heated by conducting heat from the conveyor belt to react and foam a lower portion of the prepolymer powder layer in the formation of the continuous foam bun;
• cooling means for cooling the conveyor belt and the continuous foam bun after the conveyor belt and the continuous foam bun exit the oven means to a temperature to impart sufficient integrity to the continuous foam bun to permit a skin to be removed from an upper surface of the continuous foam bun;
• and
• trimming means downstream of the cooling means for trimming the skin from the upper surface of the continuous foam bun after the continuous foam bun has been cooled by the cooling means to form a planar upper surface on the continuous foam bun.