Low-pressure plasma treatment for hydrophilization of poly(ethylene terephthalate) fabrics

Synthetic fibers are used in various industrial applications such as packaging, protective coating, and biomedical and sealing materials. However, these polymers have few polar groups. As a result, they have a weak capacity to form hydrogen bonds with water (hydrophilic groups). Hence, low-pressure plasma treatments have been proposed to modify their surface properties (hydrophobicity and wettability) by introducing polar groups or by increasing the surface roughness. In this study, we focused on a new approach to increase the hydrophilicity of poly(ethylene terephthalate) (PET) fabrics by a low-pressure plasma technique under three oxidizing atmospheres (oxygen [O2] 100%, carbon dioxide [CO2] 100%, and a mixture of O2 (50%) and CO2 (50%)). The plasma processes used in the study aimed to modify the superficial structure of polyester fibers, in particular PET, by forming new carboxyl, hydroxyl, and other polar groups on the surface. The increase in hydrophilicity was evaluated by the contact angles, the best results being 43.48 degrees for the 100% CO2 atmosphere and 44.56 degrees for the combined CO2 + O2 atmosphere. It was also confirmed by the rising height, which was determined according to the International Standard DIN 53924. The results showed an important improvement in the hydrophilicity using both the combined CO2 + O2 atmosphere and the 100% CO2 atmosphere. The surface energies of the fabrics were estimated using the contact angles. The presence of new carboxyl and hydroxyl groups was evaluated by staining methods using a cationic and a reactive dye, respectively. The results revealed an improvement in the water adsorption capacity due to the formation of carboxyl groups. Scanning electron microscope analysis of the surface morphology of the fibers showed an important cleaning action and oligomer elimination.