side by side extruders provide an extrusion apparatus which has an imposed order of longitudinal displacement of the process material in relation to itself so that cross - shearing is directed to newly aligned material in a manner which achieves volumetric blending with little unproductive shearing . the extrusion apparatus mixes and extrudes polymer like materials with as little waste shearing as possible , so as to preserve the viscosity of the polymer materials and to produce a uniformity processed material of the highest quality possible from the starting materials .