Kinetics of cold compaction of polytetrafluoroethylene-based composite material taking into account structural factors in constant force modes on press plunger or its constant speed

The article discusses the results of mathematical modeling of the one-sided pressing technological process of powder fluoropolymer materials. The peculiarity of the theoretical description is the consideration of rheodynamics, structuring and kinetics of compaction of the compressed medium. An important point of such a description is the choice of rheological equations. In what follows, it is assumed that the compaction of the material occurs according to the mechanism of viscous flow of the mass into pores (according to the theory of Ya.I. Frenkel). The rheological properties of such a medium, i.e. the ability to deform and flow, are determined by the properties of the solid phase, the presence and degree of porosity. Two variants of the technological process of pressing are considered depending on the externally specified conditions for the movement of the press plunger: modes of a constant specified force or its constant speed. The analysis of numerical calculations for each of these modes made it possible to identify their fundamental features. It was found that in the mode of a specified force, progressive autobraking of the compaction process occurs over time. It is shown that for pressing materials in both modes it is necessary to select such parameters when the time of structural transformations is longer than the compaction time. The conducted analysis allowed to develop specific recommendations for forecasting rational modes of one-sided pressing of powder materials.