The controlled preparation of secondary cells realizes the bimodal structure through two different pressure drop methods

Study on the definition, mechanism and controllability of secondary bubbles based on the bubble nucleation model in injection foaming polypropylene

“…Gong et al 34 established a radial response area model of bubble growth and showed that the growth of bubbles affects the radial migration and circumferential stretching of the surrounding resin within a certain range. Liu et al 35 proposed that in the presence of residual gas in the foaming system, slow pressure unloading and pressure fluctuations in the mold cavity would generate a gradient of critical nucleation radius, which induced the generation of secondary bubbles. This mechanism is reflected in the formation of bubble C. After the mold opening is completed, the cooling and shrinkage of the polymer melt is accompanied by a small pressure drop.…”

Customized Multimodal Cellular Elastomer Foams through Presetting Cells before CO2 Foaming

“…The formation mechanism of twostep foaming had also been systematically studied through in situ visualization. 27,28 (2) The bimodal cell structures could also be proposed by using two foaming agents with different solubility or nucleating abilities in polymers. 29,30 For instance, Zhang et al 30 which CO 2 promoted the formation of small cells, while water promoted the formation of large cells.…”

“…After the holding stage, the second nucleation would be triggered through depressurization, and then the pre-existing cells and the newly nucleated cells would grow into large cells and small cells, respectively. The formation mechanism of two-step foaming had also been systematically studied through in situ visualization. , (2) The bimodal cell structures could also be proposed by using two foaming agents with different solubility or nucleating abilities in polymers. , For instance, Zhang et al fabricated the bimodal cell structure through extrusion foaming with CO 2 and water as cofoaming agents, in which CO 2 promoted the formation of small cells, while water promoted the formation of large cells. In addition, two particulates were also added for bimodal cell structures, in which one particulate decreased water foaming time, while another particulate facilitated the nucleation rate of CO 2 .…”