During the rubber extrusions process, rubber material is processed through a screw extruding machine very similar to those used in extruding plastic.
Rubber extruders consist of a heated shearing screw conveyor or twin screw conveyor and a die through which the plasticised and pressurized rubber is squeezed. Pre-heating of the material is optional, depending on the precision of the die and the desired qualities of strength. Stock rubber material enters the screw conveyor channel, often by way of an attached hopper.
It is softened through heating and shearing, and the stock material is then pressurized through the rotation of a screw. The pressure pushes the rubber through the die, which is located at the end of the extruder. The rubber then emerges from the extruder in a profile resembling the die shape.
Die design possibilities remain nearly limitless, and rubber profiles may be extruded to small, complex hollow P-strips, sealing strips, U-channels and door seals, or they may be extruded into simple solid rubber cords.
After being extruded, the material is cured and sometimes vulcanized using various methods that include salt bath, autoclave, convection, hot air, microwave and mandrel.