Hydrophilization of polytetrafluoroethylene using an atmospheric-pressure plasma of argon gas with water–ethanol vapor

Abstract

This paper presents an approach to improve the surface wettability of polytetrafluoroethylene (PTFE) using an atmospheric-pressure plasma of argon gas with water–ethanol vapor. Plasma is generated by the dielectric barrier discharge of argon gas bubbled into a water-ethanol solution. Quadrupole mass analysis revealed that the plasma promoted the decomposition of ethanol and production of H2, CH4, and CO, which saturated at low ethanol concentrations. The modified PTFE surface was strongly influenced by the ethanol concentration in the solution and treatment time. Plasma treatment with 3%, 5% and 9% ethanol resulted in a significant reduction in the water contact angle from 115° to 16.5 ± 2.8° after 10 s of treatment. X-ray photoelectron spectroscopy showed that oxygen-containing functional groups (hydroxyl, carbonyl, and carboxyl groups) formed on the plasma-treated PTFE surface, reflecting the hydrophilization of PTFE. At the beginning of the plasma treatment, the water vapor induced the breaking of the CF2 chain, and the additional ethanol vapor generated oxygen-containing polar groups on the PTFE surface. In addition to the modification of the PTFE surface itself, a low-molecular-weight oxidized material layer was deposited over the surface, which prevented further surface modification, and the deposited layer exhibited excellent wettability. The deposited low-molecular-weight oxidized material layer was easily removed by immersion in deionized water, and the exposed modified PTFE surface exhibited stable wettability with water contact angle of 52.7 ± 3.5°.