**2.4 Analytical methods**

Prior to the measurements, fabrics were conditioned 24 hours at 20 °C and 65% relative humidity. The degree of whiteness and the colour values were measured on the Spectraflash SF600 Plus using the CIE method according to EN ISO 105-J02:1997(E) standard and EN ISO 105-J01:1997(E), respectively. Weight loss due to the pretreatments was determined by weighing the fabric samples before and after pretreatment and was expressed in percent. Water absorbency was measured according to DIN 53 924 (velocity of soaking water of textile fabrics, method for determining the rising height). Measurements of tenacity at maximum load were performed on Instron Tensile Tester Model 5567. The mean degree of polymerization (DP) was determined with the viscosimetric method in cuoxam.

Samples of remaining bleaching and scouring baths were collected after all treatments. Their ecological parameters (pH, total organic carbon (TOC), chemical oxygen demand (COD), biological oxygen demand (BOD5)) were measured, the consumption of water and energy was estimated (Preša, 2007).

#### **3. Results and discussion**

#### **3.1 Whiteness**

The achieved degrees of whiteness (W) and tint values (TV) are presented in Table 2. The desized (untreated) sample (D) had a degree of whiteness of 11.1. After alkaline scouring,

Process Conditions

**BP** - Scouring with alkaline pectinases 0.05 % Bioprep, 0.5 g/l Lawotan RWS,

**HP** - bleaching with hydrogen peroxide 7 g/l H2O2 35%, 1 g/l Cottoblanc HTD-N,

Dyeing the pre-treated fabrics was performed at 60 °C for 90 minutes with 0.5% and 2% Cibacron rot F-B. 30 g/L Na2SO4 and 8 g/L Na2CO3 was used for pale shade and 50 g/L Na2SO4 and 11 g/L Na2CO3 for medium shade. The weight of the dyed samples was 5 g. Finally, the cotton was soaped, washed and air dried. Dyeing was performed in closed

Prior to the measurements, fabrics were conditioned 24 hours at 20 °C and 65% relative humidity. The degree of whiteness and the colour values were measured on the Spectraflash SF600 Plus using the CIE method according to EN ISO 105-J02:1997(E) standard and EN ISO 105-J01:1997(E), respectively. Weight loss due to the pretreatments was determined by weighing the fabric samples before and after pretreatment and was expressed in percent. Water absorbency was measured according to DIN 53 924 (velocity of soaking water of textile fabrics, method for determining the rising height). Measurements of tenacity at maximum load were performed on Instron Tensile Tester Model 5567. The mean degree of

Samples of remaining bleaching and scouring baths were collected after all treatments. Their ecological parameters (pH, total organic carbon (TOC), chemical oxygen demand (COD), biological oxygen demand (BOD5)) were measured, the consumption of water and energy

The achieved degrees of whiteness (W) and tint values (TV) are presented in Table 2. The desized (untreated) sample (D) had a degree of whiteness of 11.1. After alkaline scouring,

polymerization (DP) was determined with the viscosimetric method in cuoxam.

**AP** - Scouring with acid pectinases

**PAA** - bleaching with peracetic acid

**AP+PAA** - one step scouring with acid pectinase and bleaching with peracetic acid

**BP+PAA** - one step scouring with alkaline pectinase and bleaching with peracetic acid.

beakers on an Launder-Ometer (Atlas).

**2.3 Dyeing procedure** 

**2.4 Analytical methods** 

was estimated (Preša, 2007).

**3.1 Whiteness** 

**3. Results and discussion** 

Table 1. The abbreviation of processes and treatment conditions

**AS** - Alkaline scouring 3 g/l NaOH, 2 g/l Cotoblanc HTD-N,

95 °C, 40 minutes

5 ml/l Forylase KL, 0.75 ml/l Foryl JA, 2 ml/l Locanit S and CH3COOH to pH 5.5, 55 °C, 40 min.

Na2CO3 to pH 8, 55 °C, 40 min.

4 g/l NaOH 100%, 95 °C, 40 min

15 ml/l Persan S15, 55 ml/l Na2CO3 0.5 M, 0.1g/l Lawotan RWS, pH 8, 55 °C, 40 min

5 ml /l Forylase KL, 0.75 ml/l Foryl JA,

0.05 % Bioprep 3000L, 0.1 mL/L Lawotan RWS, 15 mL/L Persan S15, pH 8 with NaOH, 55 °C, 40 min.

2 ml/l LocanitS, 15 ml/l Persan S15

the fibres swelled, became smoother and clean of non-cellulose impurities and the degree of whiteness increased to 19.5. However, after scouring with acidic and alkaline pectinases, both samples had lower degrees of whiteness relative to the desized sample, i.e. the sample treated with acidic pectinases (AP) had a whiteness degree of 8.2, and the sample treated with alkaline pectinases (BP) had a whiteness degree of 8.4. Negative TV values demonstrated that all scoured and desized samples had a red shade. After alkaline scouring, the red shade decreased, whereas after both bioscourings, the red shade increased.

The degree of whiteness of all scoured samples increased significantly after hydrogen peroxide bleaching. The differences in whiteness from previous scouring disappeared. Alkaline and bioscoured samples have a whiteness values above 84 and the red shade almost disappeared.

With peracetic acid bleaching, a high degree of whiteness was not achieved and the differences in whiteness from the previous scouring remained visible. The sample, which was alkaline scoured prior to bleaching (AS+PAA), had the highest degree of whiteness (72.7), whereas both bioscoured samples had lower degrees of whiteness (57.7 AP+PAA and 57.3 AP+PAA). The red shade was visible on all peracetic acid bleached samples and was more on bioscoured than on alkaline scoured fabrics, which suggests that bleaching with peracetic acid is not as effective as bleaching with hydrogen peroxide. This occurs because bleaching with peracetic acid proceeds at a low temperature and pH, where the impurities remaining after scouring could not be fully oxidised. Bioscoured fibres contained also more waxes and other impurities that hindered the successful oxidation with peracetic acid at mild conditions. Bleaching the alkaline scoured fabrics with peracetic acid is more effective since the impurities were removed from cotton fibres to a higher extent in the previous process and the pigments within fibres were more exposed to the oxidant's influence. This is confirmed by comparing data of the mass loss during treatments (Table 3).

The degrees of whiteness after a one-bath treatment (68.7 AP/PAA and 69.6 BP/PAA) were higher than those after two-bath bioscouring and bleaching with peracetic acid and close to the whiteness achieved after alkaline scouring and bleaching with peracetic acid. This can be explained by the fact that at the bleaching conditions of peracetic acid (55 °C, pH 8), hydrogen peroxide, which was present in the balanced mixture with peracetic acid, was not consumed, whereas at temperature 80 °C, which was the finite temperature of the one-bath process, hydrogen peroxide was activated, which further increased the degree of whiteness.


Table 2. Whiteness (W) and tint values (TV).

**3.3 Dyeing** 

scoured sample.

one-bath treated fabrics

0.5 % of Cibacron red F-B.

Dyeing of Environmentaly Friendly Pretreated Cotton Fabric 83

Colour strengths (expressed as K/S value) and colour differences, ∆E\*, of the fabric samples dyed with 0.5% and 2% of Cibacron red F-B are presented in Tables 4 and 6, respectively. The lightness values, L\*, croma, C\*, and hue, h, are presented in Tables 5 and 7. A standard for colour difference calculation was in each set of processes the alkaline

Scouring HP PAA Scouring/PAA

K/S ∆E\* K/S ∆E\* K/S ∆E\* K/S ∆E\*

D 4.02 - - - - - - -

AS 4.04 -a 2.61 -b 3.89 -c - -

AP 4.04 3.74 2.73 0.26 3.89 1.26 3.78 0.58

BP 4.23 3.04 2.72 0.22 4.10 0.85 3.97 0.30

a-standard for scoured fabrics, b-standard for HP bleached samples, c-standard for PAA bleached and

Table 4. Colour strengths (K/S) and colour differences (∆E\*) of the fabric samples dyed with

K/S values of all samples dyed with one concentration of dye after only scouring are similar. No significant differences were observed between the colour depths of alkaline and enzymatic pretreatments. On the contrary, colour differences between alkaline scoured and enzymatic scoured samples dyed in light shades are significant (∆E\* is above 3). This is explained by differences in whiteness after scouring, which was not covered in light shade

The colour strengths of the samples dyed after scouring and bleaching are very similar within a set of samples, but they differ between differently bleached samples. K/S values on all hydrogen peroxide bleached samples were lower than those obtained for all peracetic acid bleached samples, and this relationship exists on pale and medium-dyed samples. We can conclude that the differences in whiteness, which were visible on samples after scouring and bleaching, remained to a certain extent after dyeing. The lighter fabrics achieved lower

∆E\* values reveal that bleaching with hydrogen peroxide enabled the achievement of equal pale and medium colours on alkaline and bioscoured samples (∆E\*<0.3), while the colour differences between alkaline and bioscoured samples were higher when the samples were bleached with peracetic acid and dyed (∆E\*≈1). The colour of one-bath pretreated and dyed fabrics was close to the colour of alkaline scoured, peracetic acid bleached and dyed sample (∆E\*<0.6), which confirms that hydrogen peroxide bleaching covered the differences in

dyeing, whereas they were covered in dark shade dyeing to a greater extent (∆E\*1).

K/S values relative to darker fabrics when dyed under same conditions.

#### **3.2 Fabric properties**

Table 3 represents the loss of weight, rising height in warp direction, tenacity at maximum load and degree of polymerization (DP) of differently pretreated cotton fabric samples.

The **loss of weight** demonstrates that scouring with NaOH is more intensive and removes more incrusts than enzymatic scouring. The loss of mass after alkaline scouring was ca. 1.3% and after enzymatic scouring, was less than 1%. During hydrogen peroxide bleaching, the loss of mass was greater in those samples, where the loss of mass was lower during scouring; alkaline scoured only 0.25%, acid pectinases scoured 1.2% and alkaline pectinases scoured 0.73%. This suggests that hydrogen peroxide bleaching removed a large portion of compounds, which remained on fibres after scouring. The total mass loss after scouring and hydrogen peroxide bleaching was similar for all samples.

Peracetic acid bleaching also removed a certain part of the noncellulosic substances, which remained on fibres after scouring, but the quantity was lower relative to hydrogen peroxide bleaching. Bleaching with peracetic acid did not equalize the differences in the loss of mass, which is in agreement with the whiteness results. We can conclude that high temperature and high pH are conditions that contribute decisively to the removal of non-cellulosic impurities. Specifically, waxes cannot be removed completely when all processes are conducted at low temperatures and neutral pH, as is the case for bioscouring and peracetic acid bleaching.


Table 3. The loss of mass, rising height in warp direction, tenacity at maximum load, degree of polymerization (DP)

The remained substances influence on the water absorbency and consequently alkaline scoured samples had the highest absorbency. Bleaching improved the absorbency of the scoured fabrics, particularly of enzymatically scoured ones. However, the difference in rising height was so small, that all the samples could be considered absorbent.

There were no higher differences in **tenacity at maximum load** between the de-sized and differently treated samples. On the other hand, the results of **DP** demonstrate that bleaching with hydrogen peroxide decreased the degree of polymerization significantly, while other processes preserved the DP values close to the starting value. The bioscouring and bleaching with peracetic acid in a one bath or two bath processes causes no damage to fibers and this is one of the benefits of such processes.

#### **3.3 Dyeing**

82 Textile Dyeing

Table 3 represents the loss of weight, rising height in warp direction, tenacity at maximum load and degree of polymerization (DP) of differently pretreated cotton fabric samples. The **loss of weight** demonstrates that scouring with NaOH is more intensive and removes more incrusts than enzymatic scouring. The loss of mass after alkaline scouring was ca. 1.3% and after enzymatic scouring, was less than 1%. During hydrogen peroxide bleaching, the loss of mass was greater in those samples, where the loss of mass was lower during scouring; alkaline scoured only 0.25%, acid pectinases scoured 1.2% and alkaline pectinases scoured 0.73%. This suggests that hydrogen peroxide bleaching removed a large portion of compounds, which remained on fibres after scouring. The total mass loss after scouring and

Peracetic acid bleaching also removed a certain part of the noncellulosic substances, which remained on fibres after scouring, but the quantity was lower relative to hydrogen peroxide bleaching. Bleaching with peracetic acid did not equalize the differences in the loss of mass, which is in agreement with the whiteness results. We can conclude that high temperature and high pH are conditions that contribute decisively to the removal of non-cellulosic impurities. Specifically, waxes cannot be removed completely when all processes are conducted at low temperatures and neutral pH, as is the case for bioscouring and peracetic

> Rising height (cm)

The remained substances influence on the water absorbency and consequently alkaline scoured samples had the highest absorbency. Bleaching improved the absorbency of the scoured fabrics, particularly of enzymatically scoured ones. However, the difference in

There were no higher differences in **tenacity at maximum load** between the de-sized and differently treated samples. On the other hand, the results of **DP** demonstrate that bleaching with hydrogen peroxide decreased the degree of polymerization significantly, while other processes preserved the DP values close to the starting value. The bioscouring and bleaching with peracetic acid in a one bath or two bath processes causes no damage to fibers and this

rising height was so small, that all the samples could be considered absorbent.

D 0 18.47 2482 AS 1.27 2.9 18.45 2432 AP 0.30 2.7 16.96 2451 BP 0.89 2.5 17.95 2385 AS+HP 1.52 3.0 16.65 1774 AP+HP 1.51 3.0 17.12 1947 BP+HP 1.62 2.8 16.83 2004 AS+PAA 1.30 2.8 16.94 2278 AP+PAA 0.65 2.9 18.12 2318 BP+PAA 0.95 2.9 13.75 2399 AP/PAA 0.40 2.7 16.94 2438 BP/PAA 0.60 2.8 18.84 2300 Table 3. The loss of mass, rising height in warp direction, tenacity at maximum load, degree

Tenacity

(cN/tex) DP

hydrogen peroxide bleaching was similar for all samples.

Weight loss (%)

**3.2 Fabric properties** 

acid bleaching.

of polymerization (DP)

is one of the benefits of such processes.

Colour strengths (expressed as K/S value) and colour differences, ∆E\*, of the fabric samples dyed with 0.5% and 2% of Cibacron red F-B are presented in Tables 4 and 6, respectively. The lightness values, L\*, croma, C\*, and hue, h, are presented in Tables 5 and 7. A standard for colour difference calculation was in each set of processes the alkaline scoured sample.


a-standard for scoured fabrics, b-standard for HP bleached samples, c-standard for PAA bleached and one-bath treated fabrics

Table 4. Colour strengths (K/S) and colour differences (∆E\*) of the fabric samples dyed with 0.5 % of Cibacron red F-B.

K/S values of all samples dyed with one concentration of dye after only scouring are similar. No significant differences were observed between the colour depths of alkaline and enzymatic pretreatments. On the contrary, colour differences between alkaline scoured and enzymatic scoured samples dyed in light shades are significant (∆E\* is above 3). This is explained by differences in whiteness after scouring, which was not covered in light shade dyeing, whereas they were covered in dark shade dyeing to a greater extent (∆E\*1).

The colour strengths of the samples dyed after scouring and bleaching are very similar within a set of samples, but they differ between differently bleached samples. K/S values on all hydrogen peroxide bleached samples were lower than those obtained for all peracetic acid bleached samples, and this relationship exists on pale and medium-dyed samples. We can conclude that the differences in whiteness, which were visible on samples after scouring and bleaching, remained to a certain extent after dyeing. The lighter fabrics achieved lower K/S values relative to darker fabrics when dyed under same conditions.

∆E\* values reveal that bleaching with hydrogen peroxide enabled the achievement of equal pale and medium colours on alkaline and bioscoured samples (∆E\*<0.3), while the colour differences between alkaline and bioscoured samples were higher when the samples were bleached with peracetic acid and dyed (∆E\*≈1). The colour of one-bath pretreated and dyed fabrics was close to the colour of alkaline scoured, peracetic acid bleached and dyed sample (∆E\*<0.6), which confirms that hydrogen peroxide bleaching covered the differences in

Dyeing of Environmentaly Friendly Pretreated Cotton Fabric 85

Scouring HP PAA Scouring/PAA

L\* C\* h [°] L\* C\* h [°] L\* C\* h [°] L\* C\* h [°]

D 44.7 54.6 356.0 - - - - - - - - -

AS 45.3 56.0 356.2 46.0 58.5 357.0 46.2 57.0 356.1 - - -

AP 44.6 54.9 356.3 46.2 58.5 356.9 45.7 56.0 355.8 45.7 56.4 355.9

BP 44.1 55.0 356.4 46.2 58.4 356.9 45.4 56.4 356.0 45.7 56.6 356.0

Table 7. Lightness values (L\*) croma (C\*) and hue (h) of the fabric samples dyed with 2% of

Conventional treatment of cotton fibres was conducted in an alkaline environment: final pH at alkaline scouring and at bleaching with hydrogen peroxide was around 12.5. Such alkaline baths should be neutralized prior to drainage into the sewage system. At

While bleaching with peracetic acid and at both combined processes, the final pH value of the bath was near 6. Since neither of these processes requires neutralization of fibres, the

While scouring with pectinases and bleaching with peracetic acid, the consumption of energy required to heat the bath was also lower. Conventional processes of scouring and bleaching were performed at temperatures near the boiling point, whereas bioscouring and bleaching with peracetic acid were conducted at a temperature of 55°C. Due to the lower

The consumption of water and energy is the lowest at combined scouring/bleaching treatments. Consequently, at these processes arises the lowest amount of effluents and the

Enzymatically and alkaline scoured cotton fabrics have similar water absorbency, tenacity at maximum load and degree of polymerization. Because of lower loss of mass and lower whiteness of enzymatically scoured fabrics noticeable differences in colour occur between differently scoured samples dyed to light hues. The colour differences are overcame at

During bleaching with hydrogen peroxide the differences in whiteness arising from previous scouring processes disappeared. All samples obtained high whiteness values. At bleaching with peracetic acid the obtained whiteness values are lower and the differences

Cibacron red F-B and standard deviation in brackets.

treatment process can be shorter and less expensive.

produced wastewater is biodegradable (Preša & Tavčer, 2009).

temperature, less energy was required.

**4. Conclusions** 

medium and pale shades.

neutralization, salts that additionally load wastewaters are produced.

**3.4 Ecological parameters** 

colour arising from different scouring methods, while peracetic acid bleaching preserved those differences.

The colour evenness was excellent for all samples. The standard deviation of ten colour difference values \* *E* was below 0.06 for all dyed samples. We can conclude that all presented types of pretreatment are appropriate for further dyeing with reactive dyes, but the initial colour of the material should be considered when the dyeing recipes are prepared.


Table 5. Lightness values (L\*), croma (C\*) and hue (h) of the fabric samples dyed with 0.5 % of Cibacron red F-B.


a-standard for scoured fabrics, b-standard for HP bleached samples, c-standard for PAA bleached and one-bath treated fabrics

Table 6. Colour strengths (K/S) and colour differences (∆E\*) of the fabric samples dyed with 2 % of Cibacron red F-B and standard deviation in brackets.


Table 7. Lightness values (L\*) croma (C\*) and hue (h) of the fabric samples dyed with 2% of Cibacron red F-B and standard deviation in brackets.

#### **3.4 Ecological parameters**

84 Textile Dyeing

colour arising from different scouring methods, while peracetic acid bleaching preserved

The colour evenness was excellent for all samples. The standard deviation of ten colour difference values \* *E* was below 0.06 for all dyed samples. We can conclude that all presented types of pretreatment are appropriate for further dyeing with reactive dyes, but the initial colour of the material should be considered when the dyeing recipes are

Scouring HP PAA Scouring/PAA

L\* C\* h [°] L\* C\* h [°] L\* C\* h [°] L\* C\* h [°]

D 57.4 44.4 351.8 - - - - - - - - -

AS 58.4 46.1 351.0 59.5 48.8 350.8 59.3 47.4 350.5 - - -

AP 57.4 43.6 351.6 59.0 49.4 350.7 58.9 46.2 350.6 59.3 46.9 350.2

BP 57.7 43.9 351.8 59.1 49.3 350.9 59.1 46.6 350.4 59.4 47.2 350.3

Table 5. Lightness values (L\*), croma (C\*) and hue (h) of the fabric samples dyed with 0.5 %

Scouring HP PAA Scouring/PAA

K/S ∆E\* K/S ∆E\* K/S ∆E\* K/S ∆E\*

D 13.24 - - - - - - -

AS 13.42 -a 9.72 -b 13.38 -c - -

AP 14.17 0.84 9.57 0.03 13.10 1.15 13.19 0.81

BP 13.33 1.27 9.55 0.03 13.26 1.00 14.25 0.65

a-standard for scoured fabrics, b-standard for HP bleached samples, c-standard for PAA bleached and

Table 6. Colour strengths (K/S) and colour differences (∆E\*) of the fabric samples dyed with

2 % of Cibacron red F-B and standard deviation in brackets.

those differences.

of Cibacron red F-B.

one-bath treated fabrics

prepared.

Conventional treatment of cotton fibres was conducted in an alkaline environment: final pH at alkaline scouring and at bleaching with hydrogen peroxide was around 12.5. Such alkaline baths should be neutralized prior to drainage into the sewage system. At neutralization, salts that additionally load wastewaters are produced.

While bleaching with peracetic acid and at both combined processes, the final pH value of the bath was near 6. Since neither of these processes requires neutralization of fibres, the treatment process can be shorter and less expensive.

While scouring with pectinases and bleaching with peracetic acid, the consumption of energy required to heat the bath was also lower. Conventional processes of scouring and bleaching were performed at temperatures near the boiling point, whereas bioscouring and bleaching with peracetic acid were conducted at a temperature of 55°C. Due to the lower temperature, less energy was required.

The consumption of water and energy is the lowest at combined scouring/bleaching treatments. Consequently, at these processes arises the lowest amount of effluents and the produced wastewater is biodegradable (Preša & Tavčer, 2009).

#### **4. Conclusions**

Enzymatically and alkaline scoured cotton fabrics have similar water absorbency, tenacity at maximum load and degree of polymerization. Because of lower loss of mass and lower whiteness of enzymatically scoured fabrics noticeable differences in colour occur between differently scoured samples dyed to light hues. The colour differences are overcame at medium and pale shades.

During bleaching with hydrogen peroxide the differences in whiteness arising from previous scouring processes disappeared. All samples obtained high whiteness values. At bleaching with peracetic acid the obtained whiteness values are lower and the differences

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from previous scouring processes remained visible. This causes that the colour differences between differently scoured samples, which were bleached with hydrogen peroxide prior to dyeing, are not visually perceivable, while they remained visible on samples bleached with peracetic acid at light and medium shade dyeing.

At one-bath processes of scouring/bleaching with pectinases and peracetic acid the degree of whiteness of fabrics is higher than at two-step scouring and bleaching with peracetic acid, but lower than at bleaching with hydrogen peroxide. The colour of dyed fabrics is equal to alkaline scoured and peracetic acid bleached fabric.

The different shades obtained on differently pretreated fabrics are the consequence of their different initial whiteness values. All other parameters are very similar, the exhaustion rate, the fixation rate and the fastness properties (Preša, 2007). The bioscouring and bleaching with peracetic acid, especially the one-bath processes, are suitable treatments before dyeing with reactive dyes. Lower amount of water and energy is consumed than at conventionally pretreatment and the fibres are not damaged at all. For reproducible dyeing the initial colour of the fabric should be considered when preparing the dyeing recipes.

### **5. References**


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*Coloration Technology*, Vol.120, No.6, 311–315, ISSN 1472 - 3581

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proteases, and lipases. *Textile Chemist and Colorist*, Vol. 32, No. 5, 48–52, ISSN 0040-490X

with enzymes, organic solvents, and caustic soda on the properties of hydrogen peroxide bleached cotton yarn. *Textile Research Journal*, Vol. 68, No. 12, 920–929, ISSN

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peracetic acid at light and medium shade dyeing.

**5. References** 

0040-5175

18557366101

equal to alkaline scoured and peracetic acid bleached fabric.

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No. 8, 28–31, ISSN 1532-8813


**6** 

 *Spain* 

**Improvement in Acrylic Fibres Dyeing** 

E. Giménez-Martín, A. Ontiveros-Ortega and M. Espinosa-Jiménez *Department of Physics, EPSJ Jaén,University of Jaén, Campus "Las Lagunillas", Jaén,* 

At the interface of an electrically charged textile fabric and an aqueous solution containing an electrolyte, a surface-active agent, or a dye, an electrical double layer is set up. An electrokinetic potential or zeta potential, ζ, is developed when one of these two charged surfaces moves with respect to the other. This potential plays an important role in the electrical characterization of textile materials and in dyeing and, more generally, in many important wet processes to which textile fibers are subjected (Dai, 1994; Jacobash, 1985; Lokhande, 1970; Teli, 1993). In our opinion, the most appropriate electrokinetic technique to study the zeta potential of fibrous systems is the streaming potential method (Espinosa &Gonzalez, 1991, Gonzalez &Espinosa, 1988).Studies of the sorption of ionic and reactive dyestuff on textile fabrics shows that the electrokinetic potential and surface charge density of fibers can be influenced to a great extent by surfactant and dyes (Anders, 1965). Analysis of the solid surface free energy, together with electrokinetic measurements of the system and an investigation of the adsorption of surfactants and dyes on textiles, provides extensive information about dyeing and finishing mechanisms of fabrics (Peters, 1975). The determination of the surface free energy of a solid surface is important in a wide range of problems in pure and applied science. The surface free energy concept can be used for investigating physicochemical surface properties of textile fabrics and the results of these investigations can be correlated with important technical properties of textile applications (Grundke et al., 1991, Chibowski & Gonzalez, 1993; Holys &Chibowski, 1992; Espinosa et al., 1997; Chibowski et al. 1998). Because of the importance of acrylic fibers in textile industry, investigations in improving their dyeing properties are very interesting. In the present study, we have used as acrylic fibres samples of 100% pure Leacril fibers, of 1.3 dtex, from Montefibre S.A., Barcelona (Spain). Leacril fibers practically do not swell in water (Shukla et al., 1991). The retention of water vapor on the fibers is of the order of ca. 0.8% (Frushour & Knorr, 1985). These fibers are hydrophobic in nature, and they are not easily penetrated by the dyes ((Lokhande, 1970). The use of the surfactants to assist wetting of textile fabrics and, more particularly, for the level of dyeing has become widespread (Cegarra et al. 1984). In the present study, we have used various cationic and reactive dyes in the dyeing process of Leacril fibers. For improvement in Leacril fibers dyeing, we have used various surfactants in the pretreatment of the fibers, in order to obtain the conditions that increase the amount of dye uptaken by the mentioned acrylic fibers. On the other hand, also our purpose is to know the different physico-chemical mechanisms that govern the adsorption of different dyes onto the textile materials when these materials have been pretreated with different ionic

**1. Introduction** 

surfactants.

