**4. Methods and preparation**

Solution of TPU-DMF and its other variant of five more composite-mixed-complex formation of TPU-DMF were categorized and coded by CM-01 (TPU-DMF), CM-02 (CBP-TPU-DMF), CM-03 (TVR-TPU-DMF), CM-04 (CBP-TVR-TPU-DMF), CM-05 (NA-TVR-TPU-DMF), and CM-06 (CBP-NA-TVR-TPU-DMF).

#### **4.1 Composite mixture-1**

Tiny pellet of TPU (3%) was solubilized into DMF to form TPU-DMF solution, using a mini magnetic stirrer and an automatic shaker for 10 days in room temperature. The stirring and shaking periods were repeatedly checked and waited for maximum label of solubilization of TPU. The extended time was used for highest level of solubilization as no additional testing was implemented for this process of solubilization. TPU-DMF solution was added for each complex formation of CBP-TVR-NA.

#### **4.2 Composite mixture-2**

CBP 0.50 g and solution of 3% TPU-DMF were mixed in a beaker. It was kept on hot plate for 40 min at 80°C temperature for complex formation of CBP-TPU-DMF. TPU shell wall was kept just higher than the softening point. The droplet of TPU-DMF solution was poured into CBP until the viscous paste formation of CBP. It was continuously stirred in heating condition for making globule formation of CBP-TPU-DMF.

#### **4.3 Composite mixture-3**

The mixing process of TVR, 1.50 g and solution of 3% TPU-DMF were continued in a beaker. TVR-TPU-DMF was kept on hot plate for 40 min at 80°C temperature for complex formation. The droplet stirring process was followed for making bead formation of TVR-TPU-DMF. The droplet of TPU-DMF solution was poured into TVR until the viscous paste formation of TVR and continuously stirred for making bead formation of TVR-TPU-DMF.

#### **4.4 Composite mixture-4**

CBP 0.50 g, TVR 1.50 g, and solution of 3% TPU-DMF were mixed in a beaker and kept on hot plate for 40 min at 80°C temperature for complex formation of CBP-TVR-TPU-DMF. Firstly, the droplet of TPU-DMF solution was discharged into CBP until the viscous paste formation of CBP and continuously stirred for making bead formation of CBP-TPU-DMF. Consecutively and individually, the droplet of TPU-DMF solution was poured into TVR until the viscous paste formation of TVR and continuously stirred for making blob formation of TVR-TPU-DMF. Finally, a simultaneous complex formation was generated with the CBP-TPU-DMF and TVR-TPU-DMF (1:1) and formed a complex of CBP-TVR-TPU-DMF.

#### **4.5 Composite mixture-5**

TVR 1.50 g, NA (50%) and solution of 3% TPU-DMF were combined in beaker and heated for 40 min at 80°C temperature for complex formation of NA-TVR-- TPU-DMF. The droplet of TPU-DMF and NA solution was poured into TVR until the viscous paste formation of TVR and continuously stirred for making bead formation of NA-TVR-TPU-DMF.

#### **4.6 Composite mixture-6**

CBP 0.50 g, TVR 1.50 g, NA (50%), and solution of 3% TPU-DMF were formed as paste in a beaker and kept on hot plate for 40 min at 80°C temperature for complex formation of CBP-NA-TVR-TPU-DMF. Firstly, the droplet of NA solution and the droplet of TPU-DMF (1:1) were poured into CBP for liquid phase oxidation of CBP and bead formation of CBP-TPU-DMF. The process was continued until the viscous paste formation, continuously stirred for making bead formation of CBP-TPU-DMF. Sequentially and separately, the droplet of TPU-DMF-NA was poured into TVR until the viscous paste formation of TVR and continuously stirred for making bead formation of NA-TVR-TPU-DMF. Finally, the paste of CBP-TPU-DMF and NA-TVR-TPU-DMF were combined for complex formation of CBP-NA-TVR-TPU-DMF.

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

### **4.7 Coating on PA-6,6 fabric**

PA-6,6 fabric was cut into required sizes (width-3inch length-6inch) was uncontaminated with dipping in deionized water, then dried 50 min at 80°C in a heating chamber, and then the fabric was relaxed and cooled for 30 min at room temperature. Back part of PA-6,6 fabric was wrapped with aluminum foil paper, having thickness less than 0.2 mm for creating the artificial plain surface on the backside of fabric. This method can be repeated and applied for different types of plain roller surface of industrial coating machine. The fabric ends were tightly attached and laid on coating plate by thin adhesive paper and then the coating roller was used for hand coating system. This method was followed repeatedly for threestroke coating process for even dispersion of TPU-DMF and its other variant of five more composite-mixed-complex mixture on fabric surface. Decontaminated PA-6,6 was coated with TPU-DMF, a three-stroke coating process following first stroke coating-by second stroke coating and then third stroke coating for even dispersion of TPU-DMF. Similar coating process was thus carried out with CM-02 (CBP-TPU-DMF), CM-03 (TVR-TPU-DMF), CM-04 (CBP-TVR-TPU-DMF), CM-05 (NA-TVR-TPU-DMF) and CM-06 (CBP-NA-TVR-TPU-DMF). Also, for further research experimentation purpose, sequential overlapped coating of one formulation over other was also carried out by coating sequentially CM-2 (CBP-TPU-DMF) in first stroke coating process, and then CM-03 (TVR-TPU-DMF) coating was made on it by second stroke coating and finally then CM-04 (CBP-TVR-TPU-DMF) was coated on it by third stroke coating process. Similarly, CM-02 (CBP-TPU-DMF) was coated by first stroke coating process and then CM-03 (TVR-TPU-DMF was coated by second stroke coating and finally CM-06 (CBP-NA-TVR-TPU-DMF) was sequentially coated by third stroke coating process. All the coated PA 6,6 fabrics were dried at 60°C for 60 min to proceed for testing.

### **5. Testing methods**

#### **5.1 Color measurement spectrophotometer**

CIE, color parameters (L\*, a\*, b\*) were measured by Hunter lab reflectance spectrophotometer, Color Flex EZ; model, 45/0 LAV; under testing conditions with geometry, 45°/0°; viewing area, large; D65 illumimnant/10°standard observer; room temperature, 18°C. This hunter lab illuminant spectrophotometer uses a xenon flash lamp to illuminate the test specimen, PA-6,6. The tonal variation of PA 6,6 fabric was subjected to colorimetric evaluation for determining CIE color coordinates L\*, a\*, b\* values. The Hunter Lab reflectance spectrophotometer was calibrated in terms of highest darker and highest lighter by using standard black and white standard, for checking and matching standard values kept in machine software. To ensure sample opaqueness by minimizing the transparency of incident light; test specimen, fabric size (width-3inch length 6-inch) was single folded in lengthwise (width 3-inch length 3-inch) for placing on reflectance port.

#### **5.2 Fourier transform infrared spectrometry**

NIR scanning of treated and untreated PA-6,6 fabric was performed by FTIRS. A NIR background was standardized under diffuse reflection standard. Every sample is covered by sample cup to create reflection environment under a specified black standard, which is termed as "spectralon reflection." The sample port has sapphire/ crystal window to capture reflection of sample. Machine-specified glass vial was

**Figure 5.**

*Front view of FTIRS-NIR (a) uncovered diffuse sample port, (b) covered sample port with standardized black reference.*

used for powder sample measurement of CBP-TVR. **Figure 5a** shows the sapphire window-sample port of FTIRS-NIR. **Figure 5b** shows the sample scanning condition under machine specified black standard.

### **5.3 Scanning electron microscopy (SEM)**

Scanning electron microscopy (SEM) image was captured by TM 4000Plus model, Tabletop SEM, HITACHI, Japan. 15 KV electron acceleration was selected for every scanning of SEM. 100 magnification was performed for all image except NA treated fabric. NA-TPU-DMF and NA-TVR-TPU-DMF were captured at 25 magnifications to connote TPU effect in NA-CM-PA-6,6. Carbon conductive black tape was used for each sample mounting.
