Solid Phase Deformation Processes

Solid Phase Deformation Processes 3.1 Tensile Drawing... 

During the last ten years there have been several notable advances in the development of ultra high modulus polyethylene and polypropylene. This has been achieved most simply by tensile drawing , but also by hydrostatic extrusion , ram extrusion and die drawing all of which are solid phase deformation processes. In polyethylene, an alternative approach has been the production of fine ultra high modulus fibres from dilute solution, either by crystallisation in an elongational flow field or by stretching fine fibres spun to form a gel from dilute or reasonably dilute solution, 13 ... 

A central issue in the development of effective processes has been the increase in axial modulus with deformation ratio (i.e. draw ratio or extrusion ratio). It has been shown that all the solid phase deformation processes give oriented materials which are equivalent to a very good approximation. In polyethylene, it is of some interest to compare the measured mechanical anisotropy at 20°C and -YJ5 C with that predicted theoretically (Table 1). 

Kozlov, G. V, Aloev, V. Z., Novikov, V. U., Beloshenko, V. A., Zaikov, G. E. (2001). The Change of Deformation Mechanism and Structure in Solid-Phase Extrusion Process of Polymerization-Filled Compositions. Plast Massy, 3,21-23. 

On the other hand, the reliability of the product improves, too, if each state of the plasticity deformation, the creep deformation, and the diffusion joint in the solid phase diffusion bonding as the bonding process, is accurately understood, and the bonding process is controlled properly. 

The theoretical formulation of the collapse of a polymer chain [4,6] and the volume phase transition of gels [1-3] has been developed by utilizing an analogy between the liquefaction of a real gas and the condensation of polymer segments. In fact, this analogy is quite helpful to understand the phenomenological aspect of the collapse of a polymer chain and of a polymer network. However, we do not know to what extent this analogy is valid in reed cases. Because a gel is a solid, the elastic deformation of the network may play an important role in real phase transition processes. 

At the second and third stages, the processes involving plastic deformation of particles are developed. The smaller is particle size, the more efficient are these processes. Dispersion process is overlapped by the formation of secondary particles, while the rate of the latter process is comparable with dispersing rate thus, the surface area remains constant. Chemical reactions take place inside secondary aggregates at the contacts between particles. At the third stage, the crystallization of the products from the solid phase may occur, as well as its repeated amorphization, till some stationary state between these two is achieved. 

In all cases in the thermodynamic analysis we considered partial pressures of H2O, CO2, and other volatiles to be independent variables, if they were not related to one another by reactions. In addition the general conclusion was drawn that in thermodynamic calculations of metamorphic reactions it is impossible to assume different isotropic pressures on the solid phases and fluid. Lithostatic (nonhydrostatic) pressure or loading pressure has practically no effect on equilibrium in elastic deformation of rocks. Isotropic pressure equal to fluid pressure in the case of an excess of volatiles should be considered an equilibrium factor in actual natural processes. 

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