The polymer materials know, during the last decades, an exceptional development which is due to their interesting properties, the improvement of industrial production processes, and the possibility of its properties vary widely by various processes and methods. Among these methods which are used to improve or to vary the properties of those polymers, especially thermo-mechanical, is the equal channel angular extrusion (ECAE).

The ECAE is the promoter process among technical high plastic deformation, which produces a large deformation by simple shear when the piece passes through the bend of the die containing two channels of the same cross-sections. This process was the subject of intense study because of its ability to produce fully dense metallic materials with ultrafine grain sizes. The advantage of this technique is that it allows you to repeat the process several times while maintaining the original cross- section of the sample. The application of this process was extended to polymer materials in the 1990s.

This work involves the analysis and interpretation of the characterization test results of a polypropylene having undergone plastic deformation by the multi-pass ECAE process.

The technique of Wide-angle X-ray scattering diffraction (WAXS) is used for the microstructural characterization of the samples taken from the materials that have undergone extrusion tests under different conditions.

The method of non-contact measuring digital image correlation (DIC) is used for the displacement-measuring fields and surface deformation during mechanical characterization tests using tensile tests.

Characterization tests are performed on samples cut from the bars has undergone various extrusion methods, and behavior are studied for comparison, to see the influence of some extrusion parameters on the behavior of these materials. Calculations are made using Davis software of digital image correlation, with the ability to trace the strain fields and also the stress-strain curves.

The X-ray analysis shown us several observations that can lead us to advance the following conclusions:

- Our material has been treated by the ECAE has a certain homogeneity and isotropy according to the viewing direction. In the case where the extrusion strain rate at 10-2s-1 and without Back pressure the extruded material after the stick-slip phenomenon two bands alternating different appearance, clear and dark, where each structure which differs from one band to another has a certain homogeneity.

- Reducing the rate of extrusion and the application of back pressure has similar effects on micromolecular structure. When applied simultaneously their effects will be combined.

- The application of back pressure increases the effect of the multi-pass extrusion for the A, while it accelerates the saturation in the case of the C.

- To achieve better results extrusion, it is preferable to precede by route C with a reasonable number of passes, or by the route A but by applying a suitable back-pressure.

The comparison of the behavior of these materials with that of as-received PP allows us to observe some reduction and degradation of the mechanical properties of these materials compared to as-received PP and mainly the significant decrease of the elastic limit.

That is to say, the extrusion operation has unfortunately contributed to further deterioration especially spherulitic structure of PP, despite the tendency to increase the orientation of the macromolecular chains to the extrusion direction.

This objective will be achieved by the introduction of other parameters and factors affecting both the behavior of these polymeric materials, and also on the operation of extrusion. The factor that immediately comes to mind is the temperature.