**3.6 Fluorescence microscopy**

Figure 16 shows the results obtained from fluorescence microscopy analysis in the case of polyamide dyed with reactive dyes for cotton (Levafix Red – EBA). The dye shows a perypherical distribution in the sample without treatment (c), while in the case of the plasma treated sample the dye presents a deeper diffusion into the core of the fiber (d).

Polyamide 6.6 Modified by DBD Plasma Treatment for Anionic Dyeing Process 257

Without treatment (100ºC) - **a**

Table 8. Comparison of the maximum exhaustion for different dyeing processes.

Direct Orange 3GDL 11.7 97.9 97.4 Acid Telon MGlW 70.0 97.4 94.8 Reactive Remazol Red RB 18.9 92.0 88.2 Reactive Levafix Red EBA 48.1 97.2 93.1

The figure 17 shows the bath exhaustion behavior of the reactive dye Levafix Red, for the samples prepared with DBD discharge (b, c) and dyed at 100ºC and 70ºC respectively, compared with the untreated sample conventionally dyed at 100ºC (a). A smoothest curve and excellent bath exhaustion of 93% are observed for the optimized process performed at 70ºC.

Fig. 17. Exhaustion curves of polyamide dyeing with Levafix Red EBA dye for samples with

Table 9 shows the results of washing fastness for direct, acid and reactive dyes for the optimized dyeing of polyamide 6.6. The results of washing fastness are very good, confirming the level of dye fixation and diffusion into the fiber, despite of this process had

Direct Orange 3GDL Treated 5 4 5 5 5 4 4 Acid Telon MGlW Treated 5 4/5 5 5 5 4/5 4/5

Reactive Remazol Red RB Treated 5 4/5 5 5 5 5 5 Reactive Levafix Red EBA Treated 5 4/5 5 5 5 5 4

Table 9. Washing fastness of reactive and acid dyeing with previous DBD treatment

**Dyes Sample AC CO PA PES PAC WO Color Change** 

and without treatment dyed at 100ºC (b, a) and with treatment dyed at 70ºC (c).

**3.7.1 Washing and rubbing fastnesses** 

been performed at 70ºC.

(norm ISO 105C06/A1S)

Exhaustion (%)

(a)

(c)

(b)

With Treatment Optimized (70º) - **c**

With Treatment (100ºC) – **b**

**Dyes** 

Fig. 16. Fluorescence microscopy (Levafix Red EBA dye): a) polyamide control in bright field b) polyamide control in fluorescence field c) untreated polyamide after dyeing and d) polyamide treated after dyeing.

These results are very promising, because after the plasma treatment the dye is able to penetrate into the fiber so giving high guaranty of good fastness results.
