STUDIES OF AN AIR LUBRICATED DIE FOR EXTRUSION OF RUBBER COMPOUNDS - EFFECTS OF METAL POROSITY LEVEL AND DIE DIMENSIONS

The application of air lubrication to reduce the die pressure drop for rubber extrusion was investigated experimentally. Two compounds were used in this study. They were compounded in an internal mixer and thei r rheological properties were measured. The first was carbon-black fil led SBR which showed a yield value; the second was oil extended, black -filled SBR. Various levels of metal porosity were tested and the crit ical air pressure during air-lubricated process was determined. The cr itical air pressure decreased with increasing porosity level. Dies of varying length and diameter were investigated. A relationship for extr usion rate as a function of die pressure drop was obtained by curve fi tting. The extrudate character was investigated as a function of air p ressure.