The BC particles approach a liquid-like state in the extruder at 170 °C degrees. Using smaller particle size for BC particle could more accurately mimic this melt polymer flow in the extruder. However, too small particle size demands reducing the simulation timestep, and the liquid bridge (capillary) force may also need to be considered, which will significantly increase the overall computational cost of our simulations. When the sizes of the two simulated particles have a large gap, the smaller BC particles, which also have a lower density, will fly out from the inlet (yellow zone in Fig. ) during particle interaction, causing the model to become unstable and unable to continue. Therefore, we assume a diameter of 5 µm for BC particles.