Utilization of CO2 as a physical blowing agent for foaming of high temperature sulfone polymers. (September 2022)

• Record Type: Journal Article
• Authors: Lee, Jung H.; Chu, Raymond K.M.; Li, Ruosong; Kwan, Kermit; Park, Chul B.
• Is Part Of: Journal of CO₂ utilization. Volume 63(2022)
• Publication Date: 2022-09
• Subjects: Microcellular foam -- Polysulfone -- Polyethersulfone -- Solubility; Carbon dioxide -- Periodicals; Carbon dioxide -- Environmental aspects -- Periodicals; Carbon dioxide mitigation -- Periodicals; Carbon dioxide; Carbon dioxide -- Environmental aspects; Carbon dioxide mitigation; Periodicals; 628.53205
• DOI: 10.1016/j.jcou.2022.102131
• Languages: English
• ISSNs: 2212-9820

Abstract

Abstract: The present work adopts the one-step batch foaming technique to develop microcellular foams from polysulfone (PSU) and polyethersulfone (PES) using supercritical carbon dioxide (CO2 ) as a physical blowing agent. The results illustrates that the high temperature polymers can successfully generate highly uniform cellular structures with CO2, exhibiting cell densities in the order of 10 10 cells/cm 3 but limited volume expansion ratios of up to 4 times. The cell densities of both systems, PSU/CO2 and PES/CO2, were observed to be highly affected by the foaming pressure, showing significant enhancement of over 5 orders of magnitude with an increase in pressure from 3.4 to 13.8 MPa. On the other hand, the expansion ratio showed a strong dependence on the foaming temperature. Especially, the foams produced at pressures below 13.8 MPa exhibited a unique double peak behavior consisting of two maximum expansion ratios obtained at two different temperatures. In the temperature range of the first expansion peak, nanostructures were observed on the cell walls of the foams. The surficial features appeared in the form of a nanofibril network and gradually disappeared as the temperature approached the region of the second peak. Based on the observation, the unique double peak behavior may be correlated to the presence of the nanostructures. The work also encompassed measurement of CO2 solubility and high pressure thermal analysis of the two polymers, which were incorporated in the discussion of the distinctive foaming behavior. Highlights: Experimental and theoretical determination of carbon dioxide (CO2 ) solubility in sulfone polymers: polysulfone (PSU), and polyethersulfone (PES). Depression of glass transition temperatures of PSU and PES as a function of the dissolved CO2 content. Unique expansion behaviors of PSU and PES showing two expansion ratio maxima with respect to the processing temperature. Observation of nanostructures on the cell walls of the PSU and PES foams.