Abstract: During the extrusion of microcellular plastics, the melt flow in the pressure drop die was simulated using Ployflow software, and then the distribution of pressure and velocity and extrusion swell in the pressure drop die was studied under different CO2 concentration and melt volume flow. It was found that the melt pressure in the die increased with increasing melt volume flow, and decreased with increasing CO2 concentration. The melt average velocity at the exit was sensitive to the change of melt volume flow, but not to the change of CO2 concentration. The optimal CO2 concentration was found to be 2 wt%. The higher the melt volume flow, the less the extrusion swell.

Key words: extrusion, pressure drop die, microcellular plastics, numerical simulation, process parameters