Polytetrafluoroethylene (PTFE), classified as a high performance polymer, is mainly used for critical condition applications due to its specific properties i.e. high melting temperature, chemical resistance, low friction coefficient... However PTFE presents a weak point concerning its tribological behaviour (wear resistance), therefore it needs to be mixed with a filler or another polymer in order to reach the necessary properties for certain applications. In addition to that, due to its high viscosity (between 1010 and 1012 P) and its high processing temperature (330-350°C), PTFE cannot be processed in the classical ways (injection, extrusion…). Thus, the only processes that can be used, for un-modified PTFE, are the sintering and RAM extrusion. Through time, the crystalline behaviour of neat PTFE was the main interest of many studies, yet it is hard to find studies showing its rheological behaviour and the influence of the microstructure especially the crystalline phase on the visco-elastic properties of neat and filled PTFE, typically dynamic mechanical (DMA) and rectangular torsion analysis. In this work, our aim is to understand the effect of processing parameters such as sintering temperature, compression-molding pressure of neat and filled PTFE on its mechanical behaviour through DMA and rheological tests. The impact of the size and nature of the filler on the properties of the PTFE has also been investigated. Results have shown that all the tested parameters lead to differences in the mechanical and visco-elastic answers of the PTFE systems (neat, composites). It seems that the key factor between the mechanical properties and the microstructure remains the behaviour of the crystalline phase (size, quantity and arrangement of the crystals). This presentation aims at giving insight on these issues.