Grinding plays an important role in achieving scrap tires recycling. The batch grinding kinetics of scrap tire rubber particles in a fluidized-bed jet mill was studied based on population balance modeling. The selection and breakage functions were obtained according to the first Kapur function. It is found that these two functions were affected by the operating parameters such as the inlet gas pressure, feed load and grinding temperature. The breakage behaviors of scrap tire rubber particles under different operating conditions in the jet mill were discussed. Furthermore, a cubic function was proposed to predict the relation between the Kapur function and the particle size. The model prediction agrees well with the experimental data obtained under various operational conditions. (C) 2016 Elsevier B.V. All rights reserved.