Abstract: Taking CO2 as a foaming agent, PP/CaCO3 composite was foamed in a single screw extruder. Orthogonal method was used to design the experiment and DOE software was used to count the data. The bubble morphology on the longitudinal surface was analyzed. The impact of the processing parameters on the bubble morphology was found, and the model of average diameter, surface density, deformation, and tendency angle were solved by Design-Expert software and compared with actual experimental data. When screw speed was 42~52 r/min, die temperature was 170 ℃, melt temperature was 180~189 ℃, and content of CaCO3 was 6.67 ％~ 7.9 ％，the foamed PP/CaCO3 composite showed the best bubble morphology.

Key words: polypropylene, calcium carbonate, foaming, composite, bubble morphology, predicting model