*6.1.1.1 Coupling of TPU-DMF treated PA-6,6*

**Figure 6** (s, t) shows that polymeric coupling of PA-6,6-TPU, which are bonded with common functional group carbonyl (**Figure 7**). Structural resemblance of carbonyl and amine functional group in TPU-PA-6,6 may show the evidence of yellowish and greenish illumination on TPU treated PA-6,6 and without treated PA-6,6.

#### *6.1.1.2 Coupling of CBP-TPU-DMF treated PA-6,6*

**Figure 6** (u, v) shows the coupling among PA-6,6-CBP-TPU. CBP shows multifunctional group including carboxyl, hydroxyl, aldehyde, carbonyl, ether, and it may have other functional group including color forming groups (**Figure 8**). CBP-TPU has amino group and carbonyl group. PA-6,6 has amino group and carbonyl

**Figure 7.** *Coupling of TPU-DMF treated PA-6,6.*

**Figure 8.** *Coupling of CBP-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*

group. Amino group and carbonyl group remaining PA-6,6 surface may generate reddish and yellowish hue but the reflectance of yellowish may be weakened and, it may be turned to bluish coordinates. So, the mechanism of tonal variation on textile surface/hiding of color hue may have occurred due to multidimensional color reflection of different hue as CBP has various numbers of functional groups for different color formation on same surface. Structure of CBP surface may also vibrate the camouflage concept of illumination due to spherical surface of CBP. COOH, carbonyl group, and OH group presence in CBP may reflect reddish hue. Amine group may be an indication of yellowish hue. Therefore, color combination of CBP may show darker hue by reflecting almost black hue. When any group with colorant of yellow, blue, and red are mixed with CBP, it may hide the chromatic intensity of added colorant and makes the dull shade to the observer due to remaining multifunctional and multicolored forming group. The multifunctional mechanism of hiding tendency of color hue of CBP may be functioning as key principle of camouflage coloration on textile substances.

#### *6.1.1.3 Coupling of TVR-TPU-DMF treated PA-6,6*

**Figure 6** (w, x) shows the coupling of amide group among PA-6,6-TPU-TVR (**Figure 9**). TVR dyes has nitro group, amino group, and azo group. Nitro group may create blueish/yellowish hue, azo group may contain red/yellowish hue and amine group may prominent the yellowish reflection on the surface.

#### *6.1.1.4 Coupling of CBP-TVR- TPU-DMF treated PA-6,6*

**Figure 6** (y, z) represents the NH coupling between CBP and PA-6,6 (**Figure 10**). Benzene coupling may occur between CBP and TVR. Correspondingly

**Figure 9.** *Coupling of TVR-TPU-DMF treated PA-6,6.*

**Figure 10.** *Coupling of CBP-TVR- TPU-DMF treated PA-6,6.*

carbonyl bonding is also evidenced between TPU and PA-6,6 due to structural view in SEM magnification. TVR dyes has nitro group, azo group and amino group. PA-6,6 and TPU has also amino group. Nitro group in TVR may create bluish and yellowish hue, azo group depicts red/yellowish hue and amine group may enhance the reflection of yellow hue. CBP and TVR has similarity in benzene group and amino group. TVR encompasses nitro group and azo group, which may reflect bluish and yellowish tone, azo group may illuminate red/yellowish hue and amine group may accelerate the yellow color reflection. Hydrophilic coupling between amine group of TVR and PA-6,6 may not be happened due to absence of hydrophilic vehicle NA. CBP has COOH, OH group, amino group, and carbonyl group, which may create chromatic change of color hue with another functional group.
