The catalyst particle fragmentation process is an important step in determining the final morphology of olefin polymer particles. Understanding the different phenomena that influence it is, therefore, essential in optimizing polymerization processes and in obtaining the desired quality of polymer. A new viscoelastic model of the fragmentation process developed is demonstrated. The model relates the magnitude and generation rate of physical forces and the physical characteristics of the polymer and support. In this way, the effects of different parameters, such as reaction rate, polymer properties, and support characteristics, can be related to changes in the morphology of polymer particles. A faster reaction rate makes the particle become more porous, and a more viscous polymer will make particles with less porosity. It is discussed why larger pores will break before smaller on the same catalyst.