Plasma Jet Technology to Improve the Hydrophobicity of Flax Fabrics

Functional textiles have become demanded in modern societies regarding their protective character (flame resistance, anti-bacterial…). Hydrophobic textiles are required in clothing and housing applications mainly as anti-stain materials. They are obtained conventionally using toxic elements like Fluor or chemical processes with waste (water waste, chemicals…). In this study, we investigated the hydrophobic properties of woven textile material based on flax and treated with Si grafting assisted by atmospheric plasma technology using Hexamethyldisiloxane, and HMDSO as Monomer. This treatment presents the advantages of being eco-friendly as a process (only electrical consumption of the plasma jet machine) and as chemicals (Si is non-toxic, no waste). We varied the concentration of grafted Si on the textile surface by changing machine parameters like HMDSO flow and exposition time of textile to plasma jet. Then we investigated its hydrophobicity and resistance to washing. Observations with Scanning Electronic Microscopy (SEM) show that the coating becomes thicker for higher concentration and more extended time exposition. Nevertheless, the coating is non-continuous and remains on the surface exposed to the jet without penetrating the fiber core. This coating significantly improves the textile substrate's hydrophobicity, evidenced by contact angle goniometry. The surface tension shows a spectacular decrease with a contact angle of 150°. The treated textiles have been washed to test the permanency of the treatment after 1, 2, and 3 washing cycles. Morphological and contact angle analyses showed a decrease in the quantity of Si deposition and the contact angle, evidencing a loss in the quantity of Si molecules grafted on the surface. However, the substrate was still hydrophobic with a contact angle of 130° versus 150° respectively for washed and non-washed material. This result proves that a thin film of Si is firmly grafted to the cellulosic material.