METHODS AND APPARATUS FOR THE CONTINUOUS FORMATION OF AN EXTRUDED PRODUCT

ABSTRACT IMPROVEMENTS IN OR RELATING TO METHODS AND APPARATUS FOR THE CONTINUOUS FORMATION OF AN EXTRUDED PRODUCT Method and apparatus for the continuous formation of an extruded product from material containing fibres, molecules or other constituents susceptible to alignment or other ordered orientation. While the extrudate is still molten and moving through the die, in the direction of the extrusion axis, it is subjected to pulsating displacements in a direction transverse relative to that axis. These displacements give rise to a shearing action within the material, resulting in a degree of transverse orientation of the constituents. This orientation may be "locked" in to the extruded product when the melt solidifies, so improving the transverse strength of that product, and/or may correct an unwanted orientation that existed in the melt upstream of the point where the pulsating displacements were applied. The displacements may be applied by the synchronized operation of pistons, operating in chambers which open into the die cavity at separated locations all lying in the same transverse plane. The extrusion of products of rectangular, tubular and other sections is described, as are various methods of applying forced cooling to the die to accelerate the solidification of the molten product.