Fabrication of skinless cellular poly (vinylidene fluoride) films by surface-constrained supercritical CO2 foaming using elastic gas barrier layers

Removing the solid skin of polymer foams is a challenging approach for supercritical carbon dioxide (scCO2) foaming. Herein, a surface-constrained foaming method was used to fabricate skinless cellular poly (vinylidene fluoride) (PVDF) films. The use of organosilicone and nature latex as gas barrier layers resulted in low CO2 diffusion rates of 2.16×10-11 m2/s and 4.73×10-13 m2/s, and trigger heterogeneous nucleation of cells on the PVDF/barrier layer interface. The skin layer and the cell size gradient in the region close to the surface were successfully eliminated, and the surface cell density and cell size could be controlled in the range of 7.2×106 cells/cm3, and 13~41 μm, respectively. Moreover, the fabricated skinless cellular PVDF films exhibited an enhanced melting temperature and crystallinity due to the plasticizing effect of scCO2. The present study provides new thoughts for the fabrication of skinless polymer films using surface-constrained scCO2 foaming.