**2.3.4 Scanning electron microscopy**

Morphological modifications in samples taken from the polyamide 6.6 fabric were analysed with high resolution environmental scanning electronic microscope Schottky FEI Quanta 400FEG / EDAX Genesis X4M. The sample was mounted in aluminum specimen stubs and coated with a layer of gold.

#### **2.3.5 Atomic force microscopy**

The morphological and topographical characteristics of the polyamide surface before and after DBD plasma treatment were investigated, in a multimode SPM microscope controlled by a Nanoscope III - from Digital Instruments, equipped with an ultra light cantilever with 125 μm long by 30 μm large. The tips were silicon NHC type, with a resonance frequency from 280 to 365 kHz.

#### **2.4 Dyeing methods**

The dyeing properties were investigated using a dye-bath exhaustion process. The schemes of dyeing processes are shown in figure 2. Various dyeing tests were performed with differents parameters such as temperature, dye concentration (% w/w) and pH, in order to optimise dyeing method and conditions are presented in Table 2. Dyeings were carried out in a laboratorial "Ibelus" machine equipped with infra-red heating and the SIMCORT software was used for continuously assess dye exhaustion from the bath. The samples (each 5.0 g) were dyed with a liquor ratio of 40:1, using stainless steel dyepots with 200 cm3 capacity each.


Table 2. Parameters used in the dyeing process.

This test is performed in order to check the efficiency of the plasmatic treatment in function

Dataphysics equipment using OCA software with video system for the capturing of images in static and dynamic modes was used for the measurement of contact angles of the water

X-ray photoelectron spectroscopy analysis provides information about changes in chemical composition (elemental analysis) and chemical state (wave separation method) of atom types on the fiber surface. The VG Scientific ESCALAB 200A equipment was used to obtain

Morphological modifications in samples taken from the polyamide 6.6 fabric were analysed with high resolution environmental scanning electronic microscope Schottky FEI Quanta 400FEG / EDAX Genesis X4M. The sample was mounted in aluminum specimen stubs and

The morphological and topographical characteristics of the polyamide surface before and after DBD plasma treatment were investigated, in a multimode SPM microscope controlled by a Nanoscope III - from Digital Instruments, equipped with an ultra light cantilever with 125 μm long by 30 μm large. The tips were silicon NHC type, with a resonance frequency

The dyeing properties were investigated using a dye-bath exhaustion process. The schemes of dyeing processes are shown in figure 2. Various dyeing tests were performed with differents parameters such as temperature, dye concentration (% w/w) and pH, in order to optimise dyeing method and conditions are presented in Table 2. Dyeings were carried out in a laboratorial "Ibelus" machine equipped with infra-red heating and the SIMCORT software was used for continuously assess dye exhaustion from the bath. The samples (each 5.0 g) were dyed with a liquor ratio of 40:1, using stainless steel dyepots with 200 cm3 capacity each.

**Process Temperature (ºC) Dye concentration (%) pH**  1 100 0.05; 0.1; 1; 2 and 5 4.5 – 5.5 2 100 1 3; 4; 5; 6; 7 and 10 3 90 1 4.5 – 5.5 4 80 1 4.5 – 5.5 5 70 1 4.5 – 5.5 6 60 1 4.5 – 5.5 7 50 1 4.5 – 5.5

of the experimented dosages.

drops in polyamide 6.6 fabrics.

**2.3.2 Contact angle measurement** 

**2.3.3 X-ray photoelectron spectroscopy** 

a more detailed and complete analysis.

**2.3.4 Scanning electron microscopy** 

coated with a layer of gold.

from 280 to 365 kHz.

**2.4 Dyeing methods** 

**2.3.5 Atomic force microscopy** 

Table 2. Parameters used in the dyeing process.

Fig. 2. Dyeing conditions used for (a) Processes 1 and 2 (b) Processes 3 – 7, according with Table 2

#### **2.5 Whiteness and color strength**

The whiteness (Berger formulae) of the polyamide fabric after DBD treatment and color intensities of the dyed fabrics were measured by using a Datacolor Spectraflash SF 600 Plus CT spectrophotometer for D65 illuminant, over the range of 390-700 nm.

The average of three reflectance measurements, taken at different positions on the dyed fabric, was adopted. The relative color strength (K/S values) was then established according to the Kubelka-Munk equation, where K and S stand for the light absorption and scattering, respectively:

$$\frac{K}{S} = \frac{\left(1 - \mathbb{R}\right)^2}{2\mathbb{R}} \cdot \tag{2}$$

#### **2.6 Washing and rubbing fastnesses**

The washing fastness was evaluated in accordance with stipulated in standard ISO 105 C06, method A1S, at temperature of 40ºC. The rubbing fastness was evaluated according to standard ISO 105 X12:2001.

Polyamide 6.6 Modified by DBD Plasma Treatment for Anionic Dyeing Process 247

According to the results obtained, the dosage of 2400 W.min.m-2 is enough to obtain maximum values of K/S and minimum quantity of dye in residual bath for the three dyes, with the following working parameters in DBD machine: power of discharge -1500 W; speed - 2,5 m.min-1; nº of passages – 2. This dosage was further applied to all polyamide

Table 3 shows the difference between the wettability of the untreated and the plasmatically modified polyamide woven fabrics by measuring the time for complete water absorption

Tests **Polyamide untreated Polyamide with DBD treatment** 

The hydrophilicity of the polyamide fabric is highly improved by the plasmatic treatment in accordance with the results published by several authors for different synthetic and natural fibers, mentioning modifications in accessible polar groups at the surface and creation of

This surface modification might transform the synthetic fiber from hydrophobic to

The static and dynamic contact angle evaluation of a water droplet in the textile polyamide fabric is shown in figures 5, 6 and 7, corresponding to a mean value of five measurements.

Fig. 5. Contact of water drop in the sample without (a) and with DBD plasma treatment (b)

01 286.2 56.7 02 293.4 49.5 03 287.5 51.3 04 323.5 50.4 05 323.6 53.6

Values 302.8 52.3

Deviation 19.0 2.9 CV(%) 6.3 5.5

microporosity (Pappas et al., 2006, Oliveira et al., 2009, Yip et al., 2002).

a) b)

hydrophilic which is key point for the absorption of aqueous dye solutions.

**Time (s)** 

**3.2 Characterization of DBD treated fabrics and structural analysis** 

samples submitted to dyeing.

into the material.

Mean

Standard

Table 3. Wettability results

(time =0 s and after 30 s).

**3.2.2 Contact angle measurement** 

**3.2.1 Time of water drop absorption** 
