*6.1.1.6 Coupling of NA-CBP-TVR-TPU-DMF treated PA-6,6*

**Figure 6** (z3) shows amide linkage between CBP and PA-6,6 (**Figure 12**). Amine bonding may create between TVR and PA-6,6. Carbonyl bonding may form among CBP-TPU-PA-6,6. Oxidized carbon produces NO2 and it has been showed with

**Figure 11.** *Coupling of NA-TVR-TPU-DMF treated PA-6,6.*

**Figure 12.** *Coupling of NA-CBP-TVR-TPU-DMF treated PA-6,6.*

*Evaluation of Camouflage Coloration of Polyamide-6,6 Fabric by Comparing Simultaneous… DOI: http://dx.doi.org/10.5772/intechopen.101537*

arrow marked to mention the similar group of TVR dyes (NO2). The structure of oxidized carbon may be changed due to NA oxidation of CBP. The mechanism may influence the altering of reflection/wavelength in visible-NIR spectrum. The simultaneous combination of oxidized carbon and CBP modified PA-6,6 may replace the surface reflection significantly. The color forming functional group has been predicted the changing factors of chromatic hue. PA-6,6 has carbonyl group and amine group. TPU has also carbonyl group. Remaining unusual functional group of CBP like COOH, OH may reflect reddish hue, carbonyl group may reflect greenish/ yellowish hue and amine group may illuminate greenish/reddish hue. Spherical shape of CBP may hide the real illumination of nitro and azo group in TVR when nitro group may reflect bluish and yellowish tone and azo group may illuminate red/yellowish hue. Hence the actual prominence of hue is being decisively changed/ hided by the multifunctional tonal group of CBP.

#### **6.2 Camouflage and chromatic analysis in visible spectrum**

Established Beer–Lambert law [35] of optical absorption of material, A = εlc, A = optical absorption of materials, ε = absorptivity of the materials, l = optical path length, c = concentration of the materials. The Beer–Lambert law can be implemented for the optical absorption on PA-6,6 fabric surface in different wavelength. The variation of optical absorption of CBP can be predicted for the feasibility of camouflage coloration. Optical absorption on PA-6,6 fabric surface versus replacement of CIE color hue is proportionally related for camouflage coloration. Higher degree of optical absorption depicts the reduced intensity of chromatic hue. In this experimentation, A = optical absorption of PA-6,6 fabric surface, ε = absorptivity of CBP-TVR-TPU, I = optical path length in 400–700 nm and c = concentration of CM which are TPU-DMF, CBP-TPU-DMF, TVR-TPU-DMF, CBP-TVR-TPU-DMF, NA-TVR-TPU-DMF, NA-CBP-TVR-TPU-DMF. CIE optical absorption and reflection of chromatic hue have been studied in optical path length, 400–700 nm. The concept demonstrates that "more optical absorption on textile surface = less reflection on textile surface = altering the chromatic hue = deceiving the target detection". Therefore, CBP can create chromatic variation on textile surface and confuse the target detection to the observer. But optical path length 400–700 nm and concentration of surface CBP materials can alter the chromatic behaviors of PA-6,6 fabric. Camouflage coloration was observed in complex formation of CBP for surface hue modification of PA 6,6 fabric. The color outcome was identified based on light absorption and reflection of CIE color hue, *L\*, a\*, b\**. The reflection changing of CBP-NA-TVR-TPU-DMF treated PA-6,6 fabric was remarked in terms of CIE color coordinates. CBP-NA-TVR-TPU-DMF treated fabric showed comparatively less reflection of light and color hue hiding tendency.

#### *6.2.1 Spectrophotometric color comparison of treated PA-6,6 and untreated PA-6,6*

**Figures 13**–**16** illustrate that CBP-TPU-DMF, CBP-TVR-TPU-DMF and NA-CBP-TVR-TPU-DMF treated PA-6,6 fabric modified the light absorption and intensity of chromatic hue in CIE *L\*, a\*, b\** due to existence of CBP. The value of *L\*, a\*, b\** represents higher light absorption and minor reflection of chromatic hue, which may be elucidated the reflection changing of CBP modified PA-6,6 surface. The moderation of chromatic hue intensity identifies camouflage categories of reflection in visible range due to having a minimum value of lightness (*L\**), minimizing the value of red-green coordinates (*a\**) and blue-yellow coordinates (*b\**). **Figures 13**–**15** demonstrate that NA oxidized CBP shows maximum absorption of light than other CBP treated PA-6,6. NA oxidized NA-CBP-TVR-TPU-DMF reveals

#### **Figure 13.**

*CIE comparison of lightness hue (L\*) of treated and untreated PA-6,6 fabric.*

**Figure 14.**

*CIE comparison of greenish/reddish hue (a\*) of treated and untreated PA-6,6 fabric.*

#### **Figure 15.**

*CIE comparison of bluish/yellowish hue (b\*) of treated and untreated PA-6,6 fabric.*

CIE, *L\** = 14.33, *a\** = 0.15, *b\** = 0.30 in wavelength, 400–700 nm. CBP is practically insoluble in water. In NA-CBP-TVR-DMF, NA is functioning to form hydrophilic transformation of CBP-TVR, as well as same time TPU-DMF is performing as artificial cross-linker between CM and PA-6,6 without influencing color reflection of any other component in CM. Thus, oxidized CBP molecules may be hided the

*Evaluation of Camouflage Coloration of Polyamide-6,6 Fabric by Comparing Simultaneous… DOI: http://dx.doi.org/10.5772/intechopen.101537*

sulfonated group of TVR dyes in NA-CBP-TVR-TPU-DMF mixture whereas CBP-TVR-TPU-DMF does not exhibit hiding of red and blue color hue due to absence of NA and lacking hydrophilic reaction. CM of CBP-TPU-DMF and NA-CBP-TVR-TPU-DMF exhibit nearest of neutral value in three-dimensional CIE color coordinates. CBP-TVR-DMF mixture reveals the positive value of *a\** remaining reflection of reddish hue although theoretically the CM cannot make a complex due to absence of NA. Here, NA is not acting as hydrophilic vehicle of CBP in this CM. A proper reaction of TVR-CBP colorant may be held in between polyamide-6,6 and NA-CBP-TVR-TPU-DMF. In general theory of chromaticity, the color channel, *a\** = 0 and *b\** = 0 displays the true natural/neutral black color. The color wheel of NA-CBP-TVR-TPU-DMF shows *a\** = 0.15, *b\** = 0.30, therefore CBP has a propensity to neutral black. Similarly, NA free mixture of CBP-TPU-DMF and NA-CBP-TVR-TPU-DMF may prove minimum *L\** value due to having higher absorption of light and very minimum reflection of light. Therefore, CBP modified PA-6,6 may create a deceiving environment of color hue to the observers. Thus, a neutral or minimizing tendency of *a\** and *b\** value can create the effect of hiding reddish hue which have an outcome of declining reflection of color molecules and increasing the absorbency of light. CBP modified PA-6,6 fabric surface may conceal the reflection of remaining TVR coloring molecule of red, green, blue, yellow. CBP treated surface may be decisively reduced the formation of cone shaped receptor for visible range of color vision. Rough surface of CBP treated PA-6,6 may generate the properties of diffuse reflection. D65 light source measurement of the reflectance characteristics of CBP is the key phenomenon of camouflage have been demonstrated in visible range 400–700 nm.

#### *6.2.1.1 Spectrophotometric color combination of untreated PA-6,6 and TPU-DMF-PA-6,6*

**Figures 13**–**16**; TPU-DMF treated PA-6,6 fabric and untreated PA-6,6 fabric was compared for identification of three-dimensional chromatic hue (L\*, a\*, b\*) and its effects on PA-6,6 fabric surface. Spectrophotometric color combination of PA-6,6 shows greenish (a\* = 0.79) and yellowish (b\* = 2.1) hue, which are the nearest of

#### **Figure 16.**

*Tristimulus intensity for variations and comparison of CIE L\*, a\*, b\* and representation of spectrophotometric color combination on a (PA-6,6), B (PA-6,6 + TPU-DMF), C (PA-6,6 + CBP+ TPU-DMF), D (PA-6,6 + TVR + TPU-DMF), E (PA-6,6 + CBP + TVR + TPU-DMF), F (PA-6,6 + NA + TVR + TPU-DMF), G (PA-6,6 + NA + CBP + TVR + TPU-DMF).*

neutral hue. A maximum value of L\* = 92.29 indicates almost white color in gray hue on fabric surface. Hence color combination of PA-6,6 indicates the maximum reflection of hue. Oppositely TPU-DMF treated PA-6,6 depicts greenish (*a\** = 0.90) and yellowish (*b\** = 1.96) hue, which also identify the nearest of neutral hue. A maximum value of *L\** = 92.29 indicates almost white color/gray hue on the surface of fabric. Therefore, the color combination of TPU-DMF treated PA-6,6 also remarks the maximum reflection in CIE color coordinates. So, it can be compared that the reflection properties of CIE color hue are almost nearest/similarity in untreated PA-6,6 and TPU-DMF treated PA-6,6 fabric. It can be strongly said that TPU-DMF has minor effect on color changing. This study can be simply recommended for application of TPU-DMF for cross-linking of camouflage materials on textile surface.

#### *6.2.1.2 Spectrophotometric color combination of CBP-TPU-DMF-PA-6,6*

Complex application of CM-2 shows red (*a\** = 0.08) and bluish (*b\** = 0.84) hue which are the nearest of neutral hue. A minimum value of *L\** = 14.21 have been pointed to almost black color tone on the surface of PA-6,6 fabric. CBP-TPU-DMF treated fabric shows less reflection of color hue. It may clarify gray hue, which is tending to black and hiding the base color tone (yellow and green) of PA 6,6 fabric surface, which is replaced with opposite coordinates in color wheel.

#### *6.2.1.3 Spectrophotometric color combination of TVR-TPU-DMF-PA-6,6*

Complex application of CM-3 states reddish (*a\** = 22.45) and bluish (*b\** = 13.30) hue on PA-6,6 fabric. A maximum value of *L\** = 22.22 signifies the actual violet color of TVR on the surface of fabric. TVR added CM-03 accelerates the reddish and bluish hue.

#### *6.2.1.4 Spectrophotometric color combination CBP-TVR-TPU-DMF-PA-6,6*

CBP added CM-04 indicates minor decreasing the R/color hue in reddish and bluish hue although it seems the combination of CBP-TVR was not properly dispersed on the surface due to absence of hydrophilic vehicle, NA. Spectrophotometric color combination shows reddish (*a\** = 13.06) and bluish (*b\** = 12.95) hue on fabric surface. A maximum value of *L\** = 32.34 indicated the hiding tendency of reddish and bluish hue on the surface of fabric when CBP was mixed in CM. Even though proper reaction of complex formation was not found due to absence of NA vehicle.

#### *6.2.1.5 Spectrophotometric color combination NA-TVR-TPU-DMF-PA-6,6*

NA added CM-05 shows that reflection of color hue increases. Spectrophotometric color combination of NA-TVR-TPU-DMF depicts reddish (*a\** = 24.90) and yellowish (*b\** = 26.75) hue. A maximum value of *L\** = 28.2 indicates the increasing of reddish and bluish hue when NA was mixed in the CM. This is clarified that dyes molecules showed higher affinity with PA-6,6 when NA was mixed with TVR dyes.

#### *6.2.1.6 Spectrophotometric color combination of NA-CBP-TVR-TPU-DMF-PA-6,6*

CBP added CM-06 may be concealed the red and yellow hue of PA-6,6 surface when gray color wheel tends to black color hue. It seems that NA is functioning as *Evaluation of Camouflage Coloration of Polyamide-6,6 Fabric by Comparing Simultaneous… DOI: http://dx.doi.org/10.5772/intechopen.101537*

hydrophilic transformation of CBP-TVR into PA-6,6. Combination of CBP mixture shows more absorbency of light as per less value of *L\** . CBP modified PA-6,6 may be influenced the illumination of reflection of light/color hue. CBP modified PA-6,6 has an impact of camouflage creation and hiding factor of reddish and yellowish color under practical observation of CIE chromaticity-reflection mechanism. CBP may be acted as diminish behavior of reflection on PA-6,6 fabric surface which can create a camouflage effect of fabric under consideration CIE, *L\** , *a\**, *b\**. It can be said that NA increased the thixotropic properties of CBP-TVR colorant for good level of CBP-TVR dispersion.

#### **6.3 Camouflage and reflection comparison in NIR spectrum**

Maximum reflection percentage of CM has been summarized in **Figure 17** for comparison among raw CBP, untreated and treated PA-6,6 fabric. The original FTIR spectra has been cited in supporting information, **Figures S1** and **S2**. FTIRS was used to reveal camouflage phenomenon of CBP in terms of low reflection principle in NIR, 1000–2500 nm. The range is covered by hyperspectral camera for target detection. CBP almost absorbs all spectrum in NIR, the intensity of color forming group is very minor for target identification. A narrow reflection profile is visualized for FTIRS scanning of raw CBP and CBP treated PA 6,6 fabric. CBP treated PA 6,6 fabric was detected as low reflection materials for camouflaging in NIR. CBP has maximum number of absorptions, and it has minimum intensity which may generate low reflection chromatic signal against combat background in NIR. Reflection of CBP spectra is always lower than any other combination of PA-6,6 fabric. Comparatively TVR combination cannot decline the reflectance of PA-6,6-TPU-DMF. CBP-TVR combination can highly decrease the reflection of PA-6,6-TPU-DMF. This concept of CBP-reflection can be implemented for synthetic dyes combination with CBP. It has been clearly signified that CBP treated fabric may act as target concealment under low reflection principle in NIR spectrum.

**Figure 17.** *Comparison of maximum reflection (%) in NIR spectrum.*

#### **7. Conclusion**

L\* coordinates reflect the lightness of color intensity to the observers ranges from 0 (completely black) to 100 (completely white). The luminous intensity and degree of lightness can be perceived by the target observers in remote sensing device. The amount of CBP adsorbed on PA-6,6 surface controls a\* coordinates (red/green) and b\* coordinates (yellow/blue), which identify the lightness of color perception for CBP modified PA-6,6 fabric to the observers. Hence, CBP influences a\* coordinates for reflection of red or green hue to the target observers. Correspondingly CBP also effects on b\* coordinates, which reflect yellow or blue color tone to the observers. The intensity of object reflection modifies the perception of red, green, blue, yellow color hue to the observers. Furthermore, CBP treated PA-6,6 fabric may generate diffuse reflection to hide the color hue of combat background. SEM, color measurement spectrophotometer and FTIRS have been confirmed the low reflection coloration of PA-6,6 fabric both in visible-NIR spectrum. The experimentation on CBP based camouflage textiles can confirm the feasibility of camouflage properties development on textile substances. So, it can be suggested that CBP can be implemented for camouflage coloration of textile materials in terms of low reflection principle. CBP can be combined with synthetic dyes of camouflage design for camouflage textiles in simultaneous spectrum probe in visible-NIR. CBP may be accepted for versatile applications of weapon/vehicle coloration in terms of low reflection principle of camouflage coloration. TPU can also be recommended as a suitable cross-linking agent due to transparent property of TPU without influencing the reflection properties of CBP on PA-6,6 fabric.

#### **Acknowledgements**

Author Md. Anowar Hossain acknowledges RMIT University & Australian Government for funding through RTP Stipend Scholarship. Author acknowledges to "Professor Lijing Wang" and "Emeritus Professor Robert Shanks," School of Fashion and Textiles, RMIT University for their draft review. Author is indebted to Dr. Olga Gavrilenko and Mr. Imtiaz Ahmed Khan, Ph.D. researcher for sharing their materials to continue this research works. Author is also thankful to Ms. Shelley MacRae, technical officer (research) for her training support of SEM and FTIRS.

#### **Funding**

Author received no financial support for the research, authorship, and/or publication of this article.

#### **Declaration**

Author declare no conflict of interest to publish this article.

#### **Abbreviations**


*Evaluation of Camouflage Coloration of Polyamide-6,6 Fabric by Comparing Simultaneous… DOI: http://dx.doi.org/10.5772/intechopen.101537*

