2.3.5. Color Strength

The dyed PI yarns were knitted into single jersey circular fabric (121 g/m2). The reflectance of the dyed PI fabric was measured on a Datacolor 650 Spectrophotometers (Datacolor, Lawrenceville, NJ, USA) under the CIE Standard Illuminant D65 and the CIE 1964 10◦ Standard Observer. The color strength(K/S) of the dyed fibers was calculated from the reflectance by the Kubleka–Munk equation as shown in Equation (1),

$$\text{K/S} = \frac{\left(1.0 - \text{R}\_{\lambda}\right)^2}{2\text{R}\_{\lambda}} \tag{1}$$

where K is the absorption coefficient, S is the scattering coefficient, and R*λ* is the reflectance at a specific wavelength ( *λ*) ranging from 400 to 700 nm.

### 2.3.6. Colorfastness to Washing of the Dyed PI Fibers

The colorfastness to washing of the dyed PI fibers was tested in terms of ISO 105-C10: 2006 (https: //www.iso.org/standard/31775.html, accessed on 10 September 2017). The dyed yarns were stitched to a multifiber adjacent fabric containing wool, acrylic, polyester, polyamide, cotton, and acetate, and washed in a solution containing 5 g/L of a standard detergent (ECE) and 2 g/L of sodium carbonate at 60 ◦C for 30 min. Colorfastness rating was estimated by using the AATCC grey scale.
