Polyamide 6.6 Modified by DBD Plasma Treatment for Anionic Dyeing Processes

Abstract

Plasmatic double barrier discharge (DBD) obtained in air at atmospheric conditions is widely used, among other non-thermal plasmatic alternatives, to modify chemical and physical properties of different textile polymers (Morent et al., 2007). The impacts of DBD on environmental aspects of textile processing rise to get high attention due to important reduction of costs in dyeing by savings in processing times, products, human resources, water and energy (Carneiro et al., 2001). All fibers, from natural to synthetics, can be submitted to several irradiation methods with diverse and significant meaning in different areas of textile processing (Sparavigna, 2001). The effects on surface are reported for cellulosic fibers (Carneiro et al., 2005; Souto et al., 1996), wool (Rakowski, 1992), polyester (Oktem et al., 2000, Leurox et al., 2009), polyamide 6.6 (Papas et al., 2006; Oliveira et al., 2009), polyamide 6 (Dumitrasku & Borcia, 2006), polytetrafluoroethylene (Liu et al., 2004), polyethylene (Oosterom et al., 2006), polypropylene (Yaman et al., 2009) and meta aramid (Chen et al., 2008), being roughness, microporosity and creation of polarity by oxidation mechanisms the main modifications induced by several types of irradiation techniques. Acid dyes are the most common in use for polyamide dyeing, but some problems are very well known, as difficulties to manage uniformity and fastness. The necessary pH to achieve a good exhaustion of dye in the fiber must be carefully controlled and sometimes is excessively low. Reactive dyes are very important for the dyeing of cellulosic and protein fibers, but in polyamide the results are not equivalent due to paler colors obtained (Soleimani et al., 2006). Reactive dyes for cellulose are similar to acid dyes in their chromophoric structure, but they possess reactive groups able to react chemically with the fiber in the presence of alkali. Only few of these dyes have been developed for polyamide application with ability to react with amino groups in fiber structure without the need of alkaline fixation. Stanalan (Dystar) and Eriofast (Ciba) are well known dyes for this purpose. Reactive dyes for cotton fibers, Procion (Dystar), Kayacelon (Nippon Kayaku), and Drimarene (Clariant) were tested for polyamide dyeing at boiling temperature and different pH showing distinct results. At pH 4, the most convenient result was obtained due to a high protonation of nucleophilic amino groups, contributing to electrostatic attraction between anionic dye and positively charged fiber (Soleimani et al., 2006).