Bicontinuous Nanoporous Polymers by Carbon Dioxide Foaming

Abstract

We investigate the physical foaming process of glassy poly(ether imide) and poly(ether sulfone) using carbon dioxide and report temperature−concentration diagrams (“foam diagrams”) marking out the foaming envelope in which dense CO2-saturated films expand and microvoids are introduced. Two types of porosities are observed. Closed microcellular structures occur at carbon dioxide saturation levels below 50 cm3 (STP)/cm3 (polymer); nanoporous bicontinuous (open) structures with pore sizes as small as 40 nm occur above this CO2 concentration threshold, which is identical for both polymers. The cellular-to-bicontinuous transition is characterized in detail on the basis of gas permeation measurements and is represented as a separate window inside the foaming diagram. In this paper, the transition to bicontinuous structures is reported for the first time, and its generic physical basis is critically reviewed.

Microcellular foaming of polymethylmethacrylate in a batch supercritical CO2 process: Effect of microstructure on compression behavior

“…Foaming temperature and foaming time are the key parameters to adjust the cellular structure of the final product. 13,14 Using this process, microcellular polymers, such as polystyrene, 15 polypropylene, 16,17 polyethersulfone and polyphenylsulfone, 18,19 polycarbonate, 20 Poly (methyl methacrylate) 21 and biodegradable poly (lactic acid) have been prepared. 22 In all the cases, one of the main objectives is reducing material bulk density, reducing cell size and/or increasing the cell number density of the cellular polymer produced.…”

Superior Nanoporous Polyimides via Supercritical CO2 Drying of Jungle‐Gym‐Type Polyimide Gels

“…In particular, nanoporous polyimides containing pores on a nanometer scale are useful in a variety of fields for items such as low dielectric constant material, [1] separation membranes, [2,3] and catalyst carriers. [4][5][6] Nanoporous polyimides are produced by phase inversion, [2][3][4][5][6] CO 2 foaming, [7,8] and thermal decomposition of labile components in block copolymers. [9,10] However, the pore is limited to a spherical shape and the porosity is low.…”

Supercritical CO2 Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC

“…PP foam has been used in electronic packaging, food packaging, construction materials, traffic equipment, sports equipment, and thermal and sound insulators. The application of PP foam is determined by its mechanical properties, which are dependent on the cell structure-such as cell type, cell size, cell size distribution, and cell density-as well as the foaming rate of PP [1,[7][8][9]. Compared with traditional blowing agents, foaming using supercritical carbon dioxide (scCO 2 ) is particularly appealing, as scCO 2 can be easily dissolved in polymers, and the foaming process is environmentally friendly [9][10][11][12][13].…”