Fabrication of High Temperature Polyphenylsulfone Nanofoams Using High Pressure Liquid Carbon Dioxide

Abstract

In this paper, we describe fabrication of micro- and nano-structured foams in high temperature polyphenylsulfone (PPSU) with a Tg of 219°C using a solid-state carbon dioxide (CO2) foaming process. We have fabricated microcellular foams with cell size in 1–10 μm range, and for the first time, nanocellular foams with cell size in 20–40 nm range. We discovered a critical CO2 concentration window 10.5%–11.8%, where a rapid 2–3 orders of increase in cell nucleation density is observed and cell size drops to below 100 nm. Two approaches are demonstrated to create PPSU nanofoams with a cell size of 20–40 nm: increasing saturation pressure to 7 MPa or decreasing saturation temperature to 10°C. Both approaches use high pressure liquid CO2 and the CO2 concentration in the polymer are above the critical concentration window, which result in the formation of nanocells. At high CO2 concentration of 11.8% and 13%, as foaming temperature increases, the nanostructures transition from closed structure to an open porous structure.

Open-Celled Foams of Polyethersulfone/Poly(N-vinylpyrrolidone) Blends for Ultrafiltration Applications

“…The use of acetone induced crazing within the polymer thus resulting in a porous structure on the microcell walls. Without the use of organic solvents, Sorrentino et al [ 20 ] and Guo et al [ 21 , 22 , 23 ] developed foams with a similar structure. They investigated the foaming of high performance polymers including PESU and found that PESU exhibited nanocellular foams whereas the other investigated polymers exhibited pores with a diameter only in the micrometer range.…”

Low-density PMMA/MAM nanocellular polymers using low MAM contents: Production and characterization

“…A high saturation pressure (30 MPa) was also required in their work. As a rule, the production of nanocellular polymers using pure polymers demands extreme processing conditions, such as high pressures or low temperatures (under 0°C) [14,15,17,21]. Both approaches are difficult to scale-up to the industrial production, due to the technical requirements and costs associated to work at these conditions.…”

Understanding the role of MAM molecular weight in the production of PMMA/MAM nanocellular polymers

“…Among the diverse techniques employed for this purpose [1,12,13], foaming methods allow producing large samples without the use of organic solvents. In particular, CO 2 gas dissolution foaming has been proved to be suitable for the production of bulk nanocellular polymers using different matrices, such as poly(methyl methacrylate) (PMMA) [7,[14][15][16], polycarbonate (PC) [17], polysulfone (PSU) [18], polyphenylsulfone [19,20], or polyetherimide [21][22][23].…”