No abstract

Melt strength, pressure and the amount of gas have significant effects on the foaming of polypropylene (PP). It is convenient to study the influence of these factors on foaming effect by orthogonal test. The experiment result shows that within the set factors and levels, the improvement of melt and the concentration of foaming masterbatch has the greatest influence on the cell size and density of foamed PP, respectively. When the concentration of azodicarbonamide (ADC) is 15 %, PP/ethylene‐propylene terpolymer (EPDM) = 90:10, and SiO2 content is 3%, the foaming effect is the best. At this time, the cell diameter decreases by 42.7%, cell density increases by more than 7.5 times compared with that without optimization. Material density decreases from 0.92 to 0.56 g cm−3. It is also found that good closed‐cell structure can improve the bending and impact properties of PP in varying degrees, especially the impact strength is 55.7% higher than that of neat PP. Finally, the promoting mechanism of cell structure on mechanical properties of materials is discussed, which is of great significance for the preparation of microfoamed PP materials and the deep research of its cell structure.

No abstract