Polytetrafluoroethylene (PTFE) is widely used in industry for its remarkable properties (low friction coefficient, high thermal stability or good electrical insulation). Its processing requires specific manufacturing methods such as uniaxial cold powder compaction followed by sintering. The sintering consists in heating the PTFE blocks above the melting temperature of PTFE without any external force. The compacted blocks of PTFE are relatively large and therefore are submitted to very important strains during the sintering step due to the melting and crystallization of PTFE crystals. As crystallization is cooling rate dependent, the strain can be modified by the thermal history. This work aims to investigate the crystallization kinetics of PTFE. DSC scans, dilatometry measurements and in situ synchrotron experiments are analyzed and combined to obtain a relevant estimation of the crystallinity content evolution. Dilatometry and X-Ray experiments allow to access information on the anisotropic behavior as well as on crystalline orientation. Two crystallization mechanisms are observed: a primary crystallization that occurs almost instantly and a slower secondary crystallization. Original observations are presented on the reversibility or irreversibility of these mechanisms, and also on the evolution of the crystalline texture in regards to the crystallization.