**4. Conclusion**

A relatively low plasma dosage (DBD), around 2400 W.min.m-2, can be used to modify the surface of polyamide textile materials, leading to enhanced hydrophilicity and dyeability. Due to these modifications, dyeing of polyamide 6.6 fiber is now possible using nonconventional dyes for this fiber, such as direct and reactive dyes for cotton and wool.

The results suggest that the change in exhaustion and dyeing yield in different dyeing conditions closely correspond with the roughness´s creation and the changes in chemical oxidative properties induced by DBD treatment in polyamide fabrics. These results reflect directly on dyeing ability of the fiber providing more terminal groups to make dye bonding.

The application of anionic dyes in discharged polyamide 6.6 shows extensive improvement of dye exhaustion from baths easily achieving 100% in shorter dyeing times. The kinetics of dyeing in every case is quicker, but leveled results are obtained.

It should be noted that deeper dyeing is a great advantage for all anionic dyes since darker shades are obtainable using less amount of dyestuffs. Using plasmatic treatment in polyamide substrates it is possible to obtain decisive energetic gains by dyeing at lower temperatures, to have quite pH independent processes similar to a buffer effect and to reduce dyes and auxiliaries with deeper colors and less pollutant charges.

The DBD plasma treatment has an high industrial potential, because it is an environmental friendly dry process. Including a plasma treatment in the processing of the substrate, dyeing properties obtained by using anionic dyes are improved, namely yield, dyebath exhaustion, washing and rubbing fastness, providing a cheap, clean and high quality option for the dyeing of polyamide materials.

Another important possibility is to achieve different and wider gamut of colors in polyamide fibers provided by direct and reactive dyes, with lower energetic and processing time costs and very important environmental gains, meaning excellent opportunities to add value to new textile products.
