To determine the nature and degree of influence of process parameters, such as soap solution temperature (T), aluminum chloride solution concentration (C(AlCl3)), sample treatment time in aluminum chloride solution (t(AlCl3)) and heat treatment temperature (Ttt), on water absorption, contact angle, capillary absorption and calico moisture content, a Taguchi experiment plan was developed as shown in Table 1.
Table 1. Taguchi experiment plan
№
|
T, ℃
|
C(AlCl3), g/l
|
t(AlCl3), min
|
Ttt, ℃
|
1
|
40
|
15
|
15
|
70
|
2
|
40
|
20
|
20
|
90
|
3
|
40
|
25
|
25
|
110
|
4
|
40
|
30
|
30
|
130
|
5
|
40
|
35
|
35
|
150
|
6
|
50
|
15
|
20
|
110
|
7
|
50
|
20
|
25
|
130
|
8
|
50
|
25
|
30
|
150
|
9
|
50
|
30
|
35
|
70
|
10
|
50
|
35
|
15
|
90
|
11
|
60
|
15
|
25
|
150
|
12
|
60
|
20
|
30
|
70
|
13
|
60
|
25
|
35
|
90
|
14
|
60
|
30
|
15
|
110
|
15
|
60
|
35
|
20
|
130
|
16
|
70
|
15
|
30
|
90
|
17
|
70
|
20
|
35
|
110
|
18
|
70
|
25
|
15
|
130
|
19
|
70
|
30
|
20
|
150
|
20
|
70
|
35
|
25
|
70
|
21
|
80
|
15
|
35
|
130
|
22
|
80
|
20
|
15
|
150
|
23
|
80
|
25
|
20
|
70
|
24
|
80
|
30
|
25
|
90
|
25
|
80
|
35
|
30
|
110
|
Each experiment from the plan was carried out three times. The results of the experiments are shown in Table 2. To simplify the presentation of results, the table shows the average values of the measured properties. In graphs where there is no standard average error, the values have not changed.
Table 2. The results of the experiments
Number of experiments
|
Moisture content, %
|
Water absorption, %
|
Contact angle, º
|
Capillary absorption, mm
|
1
|
0,1
|
16,86 ± 0,33
|
149 ± 1
|
0,1
|
2
|
0,7 ± 0,48
|
21,81 ± 0,50
|
147 ± 1
|
0,1
|
3
|
14,4 ± 0,59
|
48,96 ± 1,94
|
153 ± 2
|
0,1
|
4
|
0,1
|
26,88 ± 0,15
|
156
|
0,1
|
5
|
2,6
|
21,75 ± 0,14
|
156 ± 3
|
0,1
|
6
|
0,1
|
0,55 ± 0,01
|
142 ± 3
|
2 ± 1,5
|
7
|
0,1
|
32,58 ± 1,47
|
154 ± 2
|
0,1
|
8
|
3 ± 0,15
|
32,08 ± 1,10
|
151 ± 3
|
6 ± 2,5
|
9
|
0,1
|
22,87 ± 1,26
|
143 ± 1
|
0,1
|
10
|
0,3
|
30,69 ± 0,24
|
161 ± 1
|
0,1
|
11
|
22,12 ± 2,05
|
33,51 ± 1,75
|
156 ± 2
|
6 ± 2,8
|
12
|
1,06 ± 0,57
|
27,59 ± 1,84
|
156 ± 4
|
0,1
|
13
|
0,66 ± 0,02
|
37,41 ± 3,18
|
143 ± 3
|
8,3 ± 4,5
|
14
|
1,98 ± 0,01
|
24,55 ± 1,95
|
160 ± 3
|
0,1
|
15
|
0,1
|
41,52 ± 0,29
|
151 ± 2
|
11 ± 6,5
|
16
|
2,88 ± 0,02
|
26,27 ± 0,24
|
146 ± 3
|
0,1
|
17
|
0,65
|
44,95 ± 0,38
|
139 ± 1
|
3
|
18
|
0,1
|
30,38 ± 0,18
|
150 ± 1
|
7 ± 2,5
|
19
|
0,1
|
30,51 ± 0,30
|
154 ± 3
|
5 ± 2,5
|
20
|
0,1
|
41,47 ± 0,37
|
152 ± 1
|
7 ± 2,5
|
21
|
12,96 ± 0,08
|
58,63 ± 0,49
|
152 ± 2
|
12 ± 9
|
22
|
1,71
|
41,3 ± 0,37
|
157 ± 3
|
9,7
|
23
|
4,94 ± 0,02
|
48,04 ± 0,34
|
157 ± 1
|
17 ± 8
|
24
|
6,82 ± 0,04
|
43,49 ± 0,34
|
156 ± 3
|
11,6 ± 2,5
|
25
|
0,1
|
28,8 ± 0,16
|
147 ± 1
|
13 ± 5
|
The results of measuring the hygroscopic properties of untreated coarse calico are shown in Table 3.
Table 3. Hygroscopic properties of untreated coarse calico
Propety
|
Value
|
Moisture content, %
|
80,00
|
Water absorption, %
|
48,24
|
Contact angle, º
|
0
|
Capillary absorption, mm
|
122,0
|
By comparing the data presented in Tables 2 and 3, it can be concluded that the coarse calico treatment according to the procedure described results in significant changes in the hydroscopic properties such as contact angle, moisture content and capillary absorption. With regard to water absorption, the effect of the treatment process seems almost negligible, probably because this characteristic is mainly determined by the inner porous structure of coarse calico. Thus, the obtained results show that it is the modification of the surface of coarse calico that is responsible for the observed changes in hygroscopic properties.
Based on the data presented in Table 2, the degree of influence of each process parameter (contact angle, capillary absorption, water absorption and moisture content) on the hygroscopic properties of coarse calico was calculated (Figure 2).
As one can see from Fig.2 the treatment time in the aluminum chloride solution as well as the heat treatment temperature of the samples after the treatment have the greatest effect on the contact angle within studied ranges of process parameters variation. The concentration of aluminum chloride solution has the least effect, from which it can be concluded that this parameter can be fixed and its effect can be neglected to study changes in contact angle.
Dominant influence of soap solution temperature on such a characteristic as the capillary absorption should be noted, the degree of influence of the remaining process parameters on this characteristic is approximately the same. As to the water absorption and moisture content, approximately the same degree of influence of the process parameters on these characteristics was found.
Based on the data presented in Table 3, it can be concluded that the optimal parameters for obtaining hydrophobic surfaces on coarse calico textile materials are as follows: soap solution temperature 40 °C, AlCl3 solution concentration 35 g/l, processing time 35 minutes, heat treatment temperature 150 °С.
To understand the reasons for the observed significant changes of the hygroscopic properties of coarse calico after processing, the resulting samples were analyzed by X-ray photoelectron spectroscopy. The oxygen peak in the typical XPS spectrum obtained is represented in Fig. 3.
The results of decomposition analysis of the oxygen peak of the treated samples allowed us to conclude that it is characterized by complicated structure and includes corresponding oxygen bonded with carbon (≈ 530,50-531,51 eV) and hydrogen (≈ 530,98-532,00 eV), as well as oxygen bonded with aluminum (≈ 529,98-531,80 eV). The bonds with carbon correspond to the composition of the textile material, and the bonds of oxygen with aluminum indicate the presence of aluminum oxide on the surface of the treated samples (Moulder et al. 1992). Thus, one can suggest that the hydrophobicity of the surface of the coarse calico after treatment in a solution of AlCl3 is explained by the formation of aluminum oxide films. The chemical reactions occurring during the process are discussed in detail in our previous article (Endiiarova et al. 2021). The results of SEM of the treated and untreated surface of coarse calico presented in Fig. 4 confirm this suggestion.
As one can see from Fig. 4a the untreated pristine coarse calico has a clearly woven texture consisting of smooth and near round fibers with diameter of about 10 microns and the treatment process does not change it structure (Figures 4b and 4c). The surface of untreated fibers is rather smooth (Fig. 4d), however the SEM images of the surface of treated fibers are the evidence of formation of some precipitates with composition most likely corresponding to aluminum oxide (Fig. 4e, 4f). It is interesting to note that the deposits formed during 15 minutes of treatment in AlCl3 solution had clear grain structure (Fig. 4e) however an increase in treatment time leads to formation of continuous layers (Fig. 4f). This fact allows to explain essential role of the treatment time in the aluminum chloride solution on the contact angle by decreasing of untreated surface area of the fibers with the treatment time. The strong influence of the heat treatment temperature on contact angle is probably connected with densification of the deposits with the annealing temperature. As to capillary absorption which is determined by the surface concentration of the available pores and capillaries the great effect of the fiber treatment is caused by closing the pores by depositing the oxide layer.
Therefore, it can be concluded that aluminum oxide deposits forming during processing on the surface fibers of the coarse calico do not influence the original structure of the textile material however cause significant improvement of its hydrophobic properties.