Control of the mechanical and thermal properties of semicrystalline polymers via a new processing route of the equal channel multiple angular extrusion

Abstract

Deformation routes of equal‐channel multiple angular extrusion (ECMAE) are suggested that allow realization of new combinations of positions of planes and directions of simple shear. The routes are called F, B+C, D+C. Their effect on the structure and the properties of semicrystalline polymers is studied by the example of high density polyethylene, polyoxymethylene, polytetrafluorethylene. It is demonstrated that the enhanced strength and plasticity characteristics and the reduced anisotropy of microhardness in longitudinal and transversal directions are achieved in the series: route C → routes E,F → route B+C → route D+C. The methods of X‐ray structure analysis and dilatometry revealed differences in biaxial oriented fibril structures formed after these ECMAE routes have been applied and in the character of their distribution over preferred directions of orientation. Possibility of realization of bidirectional invar‐effect in rod‐shaped billets is presented. POLYM. ENG. SCI., 54:531–539, 2014. © 2013 Society of Plastics Engineers

Reinforcing effect caused by equal channel multiple angular extrusion of polymers manufactured by the FDM process: Experimental investigation and mathematical modeling

“…However, the selection of reinforcement is also based on the cost that contributes to the total system's cost. 14 The results obtained before demonstrate application possibilities of ECMAE for structure modification of semicrystalline 15,16 and glassy 17 polymers. The basic methods of production of self-reinforced polymeric materials are cold drawing, 8 rolling, 9,10 solid-state hydrostatic or ram extrusion, 11 solution spinning, 12 and melt transformation extrusion or coextrusion.…”

“…In addition, we considered structure modification of FDM-produced layered composites made of them. 16 Here, the pairwise combined oblique deforming channels were in the perpendicular planes to be rotated about the vertical axis in increments of 908 and separated by the vertical channels. A polymeric billet (diameter 15 mm, length 50 mm) is pressed through a device composed by several pairs of channels of the same diameter intersecting at selected angles H i .…”

Specific features of plastic flow of biaxially oriented flexible-chain semicrystalline polymers

“…In ECMAE, a cylindrical billet is forced through a device consisting of several channels of the same diameter intersecting at specified angles [6]. As the deformation route, we used a route in which paired inclined deforming channels are in perpendicular planes rotating around a vertical axis at 90° intervals and are separated by vertical channels [7]. The choice of this deformation route is caused by that it enables the formation of a structure with crystallites preferably oriented parallel and perpendicular to the extrudate axis [7].…”

“…The initial speci mens and billets for ECMAE were fabricated by machining of commercially available rods. The extru sion velocity was 0.6 × 10 -3 m/s; the extrusion temper ature was 383 K (HDPE), 413 K (PP, PETP), and 423 K (PA 6); the accumulated strain was = 8.5; the strain intensity was , which corresponded to the optimal conditions of the process [7,8].…”

“…It has been shown [7,8] that, as distinct from common schemes of solid phase extrusion, such as rolling, drawing, and hydrostatic extrusion, which are characterized by a monotonous decrease in plastic parameters with an increase in accumulated strain, in the case of ECMAE, these parameters first decrease and then increase up to the respective values of unde formed specimens. The origin of this difference is in that stretching of polymers subjected to ECMAE is accompanied by successive involvement of oriented crystalline lamellae of two types in plastic flow.…”