Production of cellular polymers without solid outer skins by gas dissolution foaming: A long-sought step towards new applications

Opening Pores and Extending the Application Window: Open‐Cell Nanocellular Foams

“…More details about the influence of the gas diffusion barrier on the gas diffusivity can be found elsewhere. [36] Once the foaming procedure was concluded, the gas diffusion barrier was easily removed from the foams by introducing the samples in deionized water (room temperature) while stirring continuously for 1 h. The removal of the gas diffusion barrier was carried out before any further characterization of the obtained foams.…”

“…[35] Therefore, the regions close to the edges of the sample behave as PMMA homopolymers in terms of the solid skins formation. [36] In despite of this behavior, the high gas concentration achieved in the PBA phase allows to reduce the solid skin thickness in comparison to PMMA homopolymer. Second, the solid skin thickness analysis using M42 and M53 as preferable MAMs to be mixed with all the different PMMAs is displayed in Figure 6b.…”

“…[2] Fortunately, the solid skin drawback in polymer foams has been recently solved in our previous work. [36] A straightforward methodology to avoid the appearance of the non-foamed solid skins during the foaming stage was developed in order to expose the cellular structure to the external medium for employing them in novel applications. The skinless approach is based on the use of a gas diffusion barrier (gas diffusion barrier approach) on the polymer surfaces, that acts both as a gas retardant remaining suitable gas concentrations in the borders, and as a surface nucleator by the contact on the polymer surface.…”

“…The incorporation of the gas diffusion barrier approach to gas dissolution foaming has allowed producing polymer foams without solid skins and porous surfaces. Besides, that approximation is also useful for foaming reduced size systems regardless of the sample thickness such as thin films, microfibers, or nanoparticles, [36][37][38] achievement that has not been accomplished before without this technique.…”

“…A complete study about the nanostructuration (AFM), the stability of the cellular structure during growth (extensional rheology), the solid skin thickness analysis (scanning electron microscopy; SEM), as well as the correlation In order to avoid the appearance of the solids skins typically achieved by gas dissolution foaming, poly(vinyl alcohol) (PVOH) MOWIFLEX C17, purchased from Kuraray Europe (Hattersheim am Main, Deutschland), was employed as a gas diffusion barrier. [36] Besides, a medical grade of CO 2 (99.9% purity) was employed as a blowing agent for foaming experiments. Moreover, chloroform used in the fabrication of the solid films was purchased from Scharlab (Barcelona, Spain).…”