**4.1 Exhaust dyeing with photochromic compounds**

The group of authors of this chapter has made significant efforts in functionalizing textile fibres with photochromic dyes. Therefore, this chapter will give a review of several papers covering this issue, namely application of photochromic compounds using the means of exhaust dyeing. In the context of dyeing technology, photochromic compounds may be observed as disperse dyes appropriate for dyeing "man-made" fibres. The dyeing process has to be set accordingly.

Most of the investigation were done using Sigma Aldrich dyes of 97% purity and alterations on the level of the dye molecule were made. Selected dyes are shown in the Table 6.

From Murex Purpura to Sensory Photochromic Textiles 71

Textile samples were dyed in concentrations of 0,1%, 0,3%, 0,5% and 1% calculated according to weight of fibres. Liquor to goods ratio was set to 1:20 and pH set to 4,5. Materials were dyed according to the process scheme shown in Figure 11. Kemonecer WET

To investigate photochromic property of obtained photochromic textiles, samples were submitted to source of UV light in Solarscreen Test Camber to determine photochromic effect. Samples were irradiated in periods of 10, 20, 40 seconds and spectrophotometrically measured accordingly to determine the ability to respond to UV light. Fade was done by exhibiting in dark in the very same intervals in which the samples were irradiated. Spectrophotometric measurement was done on Datacolor, Spectraflash SF-600 CT-PLUS® Photochromic property was expressed through K/S values (eq. 3) (Fig. 13 and 14) and a\*/b\*

K/S=(1-R2)/2R (3)

Fig. 13. K/S value of PA fibre vs. concentration of the dye (\* on weight of the fibre (owof))

As seen in K/S graphs, PA is considered more suitable substrate for applications of photochromic dyes, while low obtained K/S values of PES substrate indicate this fibre unsuitable for dyeing by photochromics. Significant influence of dye concentration on

(— UV irradiated samples, --- after removal from UV source)

(non-ionic tenside) was used as an auxiliary chemical acting as an surfactant.

coordinates (Fig. 14) calculated from value of remission.

Table 6. Selected photochromic dyes

Photochromic dyes were prepared by dissolving in small quantities of acetone AC, as dissolving in acetone results in clear solutions, exhibiting photochromic reaction under UV-A (max = 354nm). Fibres chosen for the investigations were PA6 and PES, while the process of dyeing was set to satisfy the demands of disperse dyes. Exhaustion of dyes from the dyebath and onto the fibre was done according to the schematic of the process in the Figure 12. Textile substrates were dyed under laboratory conditions in Polycolor Mathis dyeing apparatus. Dyeing was commenced at 25 °C and was raised gradually to 100 °C and continued at that temperature for another 60 minutes. Textile samples were than rinsed at 40 °C, followed by hot rinsing at 80 °C.

Fig. 12. Schematic of the dyeing process

1',3'-Dihydro-8-the methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1 benzopyran-2,2'-(2H) indole]

1,3-dihydro-1,3,3 trimethylspiro[2H-indole-2,3′-(3H)naphth[2,1 b](1,4)oxazine]

D3

**t (min)**

D2

**0 20 40 60 80 100 120 140**

Photochromic dyes were prepared by dissolving in small quantities of acetone AC, as dissolving in acetone results in clear solutions, exhibiting photochromic reaction under UV-A (max = 354nm). Fibres chosen for the investigations were PA6 and PES, while the process of dyeing was set to satisfy the demands of disperse dyes. Exhaustion of dyes from the dyebath and onto the fibre was done according to the schematic of the process in the Figure 12. Textile substrates were dyed under laboratory conditions in Polycolor Mathis dyeing apparatus. Dyeing was commenced at 25 °C and was raised gradually to 100 °C and continued at that temperature for another 60 minutes. Textile samples were than rinsed at

5-Chloro-1,3-dihydro-1,3,3 trimethylspiro[2H-indole-2,3′- (3H)naphth[2,1-b](1,4)oxazine]

D1

Table 6. Selected photochromic dyes

40 °C, followed by hot rinsing at 80 °C.

**0**

Fig. 12. Schematic of the dyeing process

**20**

**40**

**60**

**80**

**100**

**120**

**T (°C)**

Textile samples were dyed in concentrations of 0,1%, 0,3%, 0,5% and 1% calculated according to weight of fibres. Liquor to goods ratio was set to 1:20 and pH set to 4,5. Materials were dyed according to the process scheme shown in Figure 11. Kemonecer WET (non-ionic tenside) was used as an auxiliary chemical acting as an surfactant.

To investigate photochromic property of obtained photochromic textiles, samples were submitted to source of UV light in Solarscreen Test Camber to determine photochromic effect. Samples were irradiated in periods of 10, 20, 40 seconds and spectrophotometrically measured accordingly to determine the ability to respond to UV light. Fade was done by exhibiting in dark in the very same intervals in which the samples were irradiated. Spectrophotometric measurement was done on Datacolor, Spectraflash SF-600 CT-PLUS® Photochromic property was expressed through K/S values (eq. 3) (Fig. 13 and 14) and a\*/b\* coordinates (Fig. 14) calculated from value of remission.

$$\mathbf{K}/\mathsf{S} = \begin{pmatrix} 1 \cdot \mathsf{R}^2 \end{pmatrix} / 2\mathsf{R} \tag{3}$$

Fig. 13. K/S value of PA fibre vs. concentration of the dye (\* on weight of the fibre (owof)) (— UV irradiated samples, --- after removal from UV source)

As seen in K/S graphs, PA is considered more suitable substrate for applications of photochromic dyes, while low obtained K/S values of PES substrate indicate this fibre unsuitable for dyeing by photochromics. Significant influence of dye concentration on

From Murex Purpura to Sensory Photochromic Textiles 73

**-35**

**b\***

**b\***

**0 5 10 15 20 25 30 35**

D1 D2 D3 Fig. 15. a\*/b\* coordinates of PA samples dyed by 1% (owof) of photochromic dye

During the last ten years the traditional textile industry, that during the decades has favored quality, has changed its strategy to support the innovation and the creation of new products and functionalities. Accordingly, a rapidly growing trend is noticeable in the field of smart fabrics and intelligent textiles that can sense and react to environmental conditions or stimuli from mechanical, thermal, chemical, electrical or magnetic sources. Research by this group of authors supports and represents a contribution to the field of testing and optimization applications of photochromic dyes in textiles. In the future, research of the authors will be aimed at analyzing photochromic textile materials using state of the art instrumental analyses, such as FTIR and HPLC, supported by different spectrophotometric methods. Potentials of these materials will be researched in terms of sensory properties, with emphasis on their accuracy to react in preprogrammed manner to a very specific level of ultraviolet irradiation. Relationship among colour strength and UV irradiation levels will be researched using statistically designed experiments. In terms of application methods, screen printing will be given most attention, this statement being supported by the fact that presence of photochromic dyes or pigments is needed only on the surface of the textile material. This would well broaden the number of substrates, whereas in dyeing, only a small number is really suitable. In regards to the price of the final product, printed substrates should be favoured due to their obvious economical viability and feasibility. In terms of ecology, exemption of wastewater should be

In terms of "high added value" photochromic textiles should be considered as such, while the number of functions is increased significantly when compared to conventional textiles. Colour phenomenon is used to sense and detect harmful UV rays, while it is only exhibited under irradiation of UV light. Therefore, one can speak of colour at the right time, rather than of colour all the time. Dyes described in this paper may also provide necessary protection from UV spectra, while the energy is used for rearrangements on molecular level of the dye, thus increasing the number of conjugated double bonds, which is experienced as

From this paper one could conclude great potentials of such dyes as described in this paper. Research and results shown imply to broadened use of photochromic dyes and expansion

possibilities from ophthalmics to virtually any polymer if applied properly.

**a\***

**a\***

**-30 -25 -20 -15 -10 -5 0**

**b\***

**-30 -25 -20 -15 -10 -5 0**

**-25**

**-15**

**-5**

**-35 -25 -15 -5 5**

**5. Conclusion** 

advantageous over dyeing.

colour.

**a\***

**5**

obtained K/S values was obtained with maximum value (K/S≈8) reached after 20 seconds UV irradiation time for PA sample dyed by 1% of Dye 1. Dyeing by Dye 3 resulted in colored substrates (PA and PES) of distinct photochromic property expressed through increased K/S values measured at same wavelength (maxPA = 600 nm).

Fig. 14. K/S value of PES fibre vs. concentration of the dye (\* on weight of the fibre (owof)) (— UV irradiated samples, --- after removal from UV source)

Low K/S value obtained for PES fibres confirm the influence of fibres structure on effectiveness of the dyeing process which was found to be appropriate for PA fibres, while in the case of PES carrier should have been added or process carried out at higher temperature then 100 °C. Ideally, this would increase the volume of amorphous area in PES by decreasing crystallinity. Because of low obtained values for PES fibres only a\*/b\* coordinates for PA fibres are shown (Fig. 15).

Shown a\*/b\* graphs refer only to PA samples dyed by the greatest investigated amount of dye (1% owof) (Fig. 15).

Lowest color depth was obtained in PA samples dyed by D1. After exposition to UV, lightness of the samples (D1-PA) increases, while chromacity is less than in samples dyed by D2 and D3, although difference in chromacity of UV irradiated and unirradiated sample is greatest in PA samples dyed by D1. Aforesaid, suggests the advantage of subjective reasoning over reading instrumental data only.

Fig. 15. a\*/b\* coordinates of PA samples dyed by 1% (owof) of photochromic dye

### **5. Conclusion**

72 Textile Dyeing

obtained K/S values was obtained with maximum value (K/S≈8) reached after 20 seconds UV irradiation time for PA sample dyed by 1% of Dye 1. Dyeing by Dye 3 resulted in colored substrates (PA and PES) of distinct photochromic property expressed through

Fig. 14. K/S value of PES fibre vs. concentration of the dye (\* on weight of the fibre (owof))

Low K/S value obtained for PES fibres confirm the influence of fibres structure on effectiveness of the dyeing process which was found to be appropriate for PA fibres, while in the case of PES carrier should have been added or process carried out at higher temperature then 100 °C. Ideally, this would increase the volume of amorphous area in PES by decreasing crystallinity. Because of low obtained values for PES fibres only a\*/b\*

Shown a\*/b\* graphs refer only to PA samples dyed by the greatest investigated amount of

Lowest color depth was obtained in PA samples dyed by D1. After exposition to UV, lightness of the samples (D1-PA) increases, while chromacity is less than in samples dyed by D2 and D3, although difference in chromacity of UV irradiated and unirradiated sample is greatest in PA samples dyed by D1. Aforesaid, suggests the advantage of subjective

(— UV irradiated samples, --- after removal from UV source)

coordinates for PA fibres are shown (Fig. 15).

reasoning over reading instrumental data only.

dye (1% owof) (Fig. 15).

increased K/S values measured at same wavelength (maxPA = 600 nm).

During the last ten years the traditional textile industry, that during the decades has favored quality, has changed its strategy to support the innovation and the creation of new products and functionalities. Accordingly, a rapidly growing trend is noticeable in the field of smart fabrics and intelligent textiles that can sense and react to environmental conditions or stimuli from mechanical, thermal, chemical, electrical or magnetic sources. Research by this group of authors supports and represents a contribution to the field of testing and optimization applications of photochromic dyes in textiles. In the future, research of the authors will be aimed at analyzing photochromic textile materials using state of the art instrumental analyses, such as FTIR and HPLC, supported by different spectrophotometric methods. Potentials of these materials will be researched in terms of sensory properties, with emphasis on their accuracy to react in preprogrammed manner to a very specific level of ultraviolet irradiation. Relationship among colour strength and UV irradiation levels will be researched using statistically designed experiments. In terms of application methods, screen printing will be given most attention, this statement being supported by the fact that presence of photochromic dyes or pigments is needed only on the surface of the textile material. This would well broaden the number of substrates, whereas in dyeing, only a small number is really suitable. In regards to the price of the final product, printed substrates should be favoured due to their obvious economical viability and feasibility. In terms of ecology, exemption of wastewater should be advantageous over dyeing.

In terms of "high added value" photochromic textiles should be considered as such, while the number of functions is increased significantly when compared to conventional textiles. Colour phenomenon is used to sense and detect harmful UV rays, while it is only exhibited under irradiation of UV light. Therefore, one can speak of colour at the right time, rather than of colour all the time. Dyes described in this paper may also provide necessary protection from UV spectra, while the energy is used for rearrangements on molecular level of the dye, thus increasing the number of conjugated double bonds, which is experienced as colour.

From this paper one could conclude great potentials of such dyes as described in this paper. Research and results shown imply to broadened use of photochromic dyes and expansion possibilities from ophthalmics to virtually any polymer if applied properly.

From Murex Purpura to Sensory Photochromic Textiles 75

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