Air-Lubricated Die for Extrusion of Rubber Compounds

Abstract

Abstract The flow of a rubber compound through a die is an essential step of a rubber extrusion operation. The die forms the compound into the desired shape. In many cases, the output of the extruder is limited by the resistance of flow in the die. Too high pressure losses in the die may additionally result in an excessive increase of the temperature, and unwanted crosslinking of the rubber compound may occur. Various possibilities are available to reduce the resistance of flow in the die. The simplest one is elevation of the processing temperature, which leads to reduction of viscosity. This can be done, however, only within some limit. Reduction of the pressure losses in the die may also be achieved by decreasing the die length, but this option produces larger swelling. Other more innovative procedures may be suggested. Evidence exists that the pressure losses in the die can be reduced by introducing sound or ultrasonic waves of high intensity into the die zone. In this paper, we present what we believe is a new idea, another option of decreasing a resistance of flow of the rubber compound in the die. This is achieved by injecting air between the rubber compound and the wall of the die. This paper continues the experimental studies of the authors on the flow of rubber compounds in dies and screw extruders.