Treatment of PET nonwoven with a water vapor or carbon dioxide plasma

Gas plasma treatment of poly(ethylene terephthalate) nonwoven (NW–PET) was used to increase the hydrophilicity of single- and multilayer NW–PET. NW–PET was treated with a pulsatile CO2 or with a pulsatile H2O glow discharge. X-ray photoelectron spectroscopy (XPS) showed significantly more oxygen with CO2 glow-discharge-treated NW–PET than with H2O glow-discharge-treated-NW–PET surfaces. Moreover, the introduction rate of oxygen at a single layer of NW–PET was higher for a CO2 than for a H2O glow-discharge treatment. Titration data revealed significantly higher surface concentrations of carboxylic groups for CO2 glow-discharge NW–PET than for H2O glow-discharge-treated NW–PET. Mass spectrometry analysis revealed that the entire internal surface of a single layer of NW–PET was modified. XPS and contact measurements confirmed the modification of the internal surface of multilayers of NW–PET. H2O and CO2 glow-discharge-treated substrates consisting of six layers of NW–PET had a nonuniform surface concentration of carboxylic acid groups as determined with titration experiments. The outside layers of the substrate contained a higher surface concentration of carboxylic acid groups than did the inside layers. XPS analysis and titration data showed that the rinsing of H2O and CO2 glow-discharge-treated NW–PET with water changed the surface composition considerably. Part of the carboxylic acid group-containing species were washed off.