Solid‐State Extrusion

Abstract

AbstractSolid‐state extrusion (SSE) is a method for attaining a highly oriented state of polymers, and is based on polymer deformation at temperatures just below the polymer melting temperature, or for amorphous polymers just above the glass‐transition temperature mainly by extrusion through conical or slit dies.SSE is used for shape forming and structure modification of various polymer materials (homopolymers, polymer blends, filled polymer composites) and makes it possible to produce fibers, films, pipes, shapes including those of large cross section and of different configurations, possessing high strength–stress characteristics.In this article, much attention is given to the most known SSE versions—plunger extrusion and hydrostatic extrusion with the information on the influence of process controlling parameters on extrusion pressure, velocity of product exiting, value of extrudate swell, structure and properties of the processed material. There exists a region of controlling parameters where the process is stable; outside the region, the polymer flow is discontinuous, extrudate shape is imperfect and, finally, its failed.Two new techniques of SSE are presented in brief, namely the equal channel angular extrusion and the twist extrusion which, in contrast to the conventional ones, are based on polymer simple shear, not drawing. These techniques are found to be promising for structure modification of polymers.