Tensile and impact properties of microcellular isotactic polypropylene (PP) foams obtained by supercritical carbon dioxide

A new promising nucleating agent for polymer foaming: effects of hollow molecular-sieve particles on polypropylene supercritical CO2 microcellular foaming

“…The samples were saturated at 20 MPa and foamed at 154 C for 10 s. As expected, the pure PP foam presented poor cellular structure and obvious cracked cells. 27 In contrast, PP/ MS (0.5%), PP/MS (2.0%), and PP/MS (5.0%) foams exhibited more uniform cell distribution, smaller cell size, a regularpolygon cell shape, and well-dened cell walls. The cells were strongly contacted by the junction regions of three contacting cells of the different-content PP/MS foams.…”

“…The outstanding structural parameters of PP/MS foams indicate good mechanical properties for many applications. 8,10,27 It can be clearly seen in Fig. 2 that the cell-size distribution of the PP/MS foam becomes narrower than that of the pure PP foam, which indicates that the presence of MS particles improves the cellular structure of PP/MS foams greatly, resulting in a uniform cell size in the obtained foams.…”

Grafting dual polar monomers onto hydroperoxidized polypropylene with the assistant of supercritical carbon dioxide

“…Most of all, scCO 2 swells polymer but not dissolve it. In this way, the diffusion resistance is reduced and the solute may be dissolved and distributed more homogeneous in the amorphous domains of the bulk polymer [14][15][16][17][18][19].The density of scCO 2 is continuously tunable from gas to liquid by changing its temperature or pressure. This provides the ability to control the degree of swell of a polymer [15,18].…”

“…In one-step process, polar monomers and initiator dissolved in scCO 2 are carried into PP matrix, simultaneously thermal free-radical grafting polymerization, resulting in composites [14,16,[18][19][20][21]. This is a simple technical art, but in this course CO 2 is retained in the system from beginning to end.…”

“…The pressure in reactor increases rapidly with temperature, which is not favorable to product in large scale. Two-step process is reported as follows [10,[17][18][19]: first, monomers and initiator dissolved in scCO 2 are carried into PP matrix; thereafter, CO 2 is discharged and the monomers and initiator would be left in the polymer; at last, thermal free-radical grafting polymerization is achieved in mild condition. However, grafting reaction and auto-polymerization of monomers occur at the same time.…”