In this study the mechanical performance of the different polymorphs of isotactic polypropylene, typically present in iPP crystallized under industrial processing conditions, are assessed. Different preparation strategies were used to obtain samples consisting of almost solely alpha, beta or gamma crystals. X-ray measurements were used for validation. The intrinsic true stress-true strain response in uniaxial compression, as well as its dependence on temperature and strain rate (deformation kinetics), was determined for all individual phases. Moreover, measurements were not only performed at elevated temperatures, but also at temperatures lower then room temperature. The obtained yield stresses were plotted as a function of strain rate and described with a modification of the Ree-Eyring equation. Differences and similarities observed in the deformation kinetics will be shown and discussed. Furthermore the presence of three deformation processes, acting in parallel, is revealed. The Ree-Eyring equation enabled us to do life time predictions under well-defined thermal and mechanical conditions. In addition, these predictions were experimentally validated using constant load tests in uniaxial compression.