Microcellular injection molding of neat isotactic polypropylene (iPP) and isotactic polypropylene/nano-calcium carbonate composites (iPP/nano-CaCO

3

H) was performed using supercritical carbon dioxide as the physical blowing agent. The influences of filler content and operating conditions on microstructure morphology of iPP and iPP/nano-CaCO

3

H microcellular samples were studied systematically. The results showed the bubble size of the microcellular samples could be effectively decreased while the cell density increased for iPP/nano-CaCO

3

H composites

especially at high CO

2

concentration and back pressure

low mold temperature and injection speed

and high filler content. Then Moldex 3D was applied to simulate the microcellular injection molding process

with the application of the measured ScCO

2

solubility and diffusion data for iPP and iPP/nano-CaCO

3

H composites respectively. For neat iPP

the simulated bubble size and density distribution in the center section of tensile bars showed a good agreement with the experimental values. However

for iPP/nano-CaCO

3

H composites

the correction factor for nucleation activation

energy F and the pre-exponential factor of nucleation rate f0 were obtained by nonlinear regression on the experimental bubble size and density distribution. The parameters F and f0 can be used to predict the microcellular injection molding process for iPP/nano-CaCO

3

H composites by Moldex 3D.