Equal‐channel multiangular extrusion of semicrystalline polymers

Abstract

Potentialities of a new simple shear-based scheme of the solid-phase extrusion of polymers, named the equal channel multiple angular extrusion (ECMAE), for modification of semicrystalline polymer structure have been investigated by the example of low-and highdensity polyethylene (LDPE, HDPE), polyamide-6 (PA-6), and polytetrafluoroethylene (PTFE). The effects of velocity and extrusion temperature, plastic deformation intensity, and accumulated equivalent plastic strain value on properties of a number of crystallizing polymers have been studied. It has been shown that the highest strength characteristics are attained for the extrusion temperatures of (0.8-0.95) of the melting temperature and deformation velocity of (0.6-1.1) mm s 21 . For the ECMAE-processed specimens, the density, the enthalpy, and the melting temperature have become higher. In the oriented structure of semicrystalline polymers formed by the ECMAE, the lamellae are oriented along the extrudate axis.

Modification of polyamide-6 structure by combined methods of solid-phase extrusion

“…The extrusion rate was equal to 0.6 × 10 −3 m/s and the extrusion temperature was 423 K. These were the optimum conditions of the process [8]. PA-6 (ERTANOL 6SA, QUADRANT) was the object of our research.…”

“…For ECMAE, the deformation intensity 1 is in the range 0.54-0.83 and the accumulated strain value ε ECMAE is in the range 1.3-6.7. where i is the half-angle of channel intersection and n the number of channel intersection angles [8]. ED with the accumulated strain value is given as follows:…”

“…The accumulation of plastic deformations is not, in the present case, accompanied by changes in geometry of the polymer billet; it is attained due to increasing the number of passes through the intersecting channels. We have recently shown the efficiency of the equal-channel multiple angle extrusion (ECMAE), which is a modified version of ECAE, in improving the set of physical and mechanical properties of crystallizing polymers [8]. In the ECMAE plant, there are several zones of shear deformation providing the accumulation of high plastic deformations in one cycle of the process.…”

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

“…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.…”