Atmospheric pressure plasma treatment of polyurethane foams with He–O2 fed dielectric barrier discharges

The atmospheric pressure non-equilibrium plasma treatment of open-cell polyurethane foams is carried out using dielectric barrier discharges fed with helium and oxygen mixtures. During plasma processes, the discharge is ignited both outside the foam and within its porous structure to achieve the three-dimensional surface modification of the entire substrate. X-ray photoelectron spectroscopy results reveal the uniform functionalization of both the exterior and interior surfaces of the porous material with oxygen-containing groups. In addition, nuclear magnetic resonance spectroscopy analyses confirm that surface chemical modification occurs with preservation of the foam polymeric skeleton. Scanning electron microscopy observations and water contact angle measurements show that the plasma-treated foams exhibit increased surface roughness and wettability, respectively. It is also observed that aging of the plasma-treated foams is more pronounced in water than in air, due to the inevitable dissolution of oxidized polymer fragments formed during plasma exposure. Finally, it is found that a simple post-processing step improves the capability of the plasma-treated foams to remove heavy metal ions from water, as demonstrated through Cd2+ adsorption experiments.