Coming to the extrusion process of rubber, the rubber compound including polymers, various types of additives and fills like curing agents antioxidants, pigments are fed into the extruder. The extruder typically consists of a rotating screw inside a closely fitted heated barrel. The primary purpose of the extruder is to do three things a) soften, b) mix, c) pressurize the rubber as it is fed continuously fed to die at the extruder exit. A schematic of the extruder is shown below.


Die is a sort of metal disk that has a machined opening in the desired shape of the part that needs to be extruded. The rubber already softened by heating is then forced by the rotating screw through the die opening into the shape of the profile cut in the die. A typical phenomenon called die swell takes place as the rubber shape leaves from the die. Because of this the part cross-section becomes larger than the die cross-section. The part cross-section depending on the material may rise up to several folds over the die.

Subsequently the processes of vulcanization or curing takes place as the last step in the extrusion process. This aids the rubber extruded profiles to maintain its shape and acquire necessary physical properties. The image shown below is of a typical Rubber extrusion line.