2.1.1. Materials Fabric used in this experiment includes commercially scoured-bleached 100% cotton knitted single jersey structure having areal density of 175 grams per square meter. Fabric was collected from “HI-FASHION COMPOSITE TEXTILES LTD”, Joydeppur, Gazipur, Bangladesh. One hundred percent cotton 22.7 tex combed yarn was used to manufacture the fabric. The fabric has the following geometrical properties: course per inch (CPI) = 48, Wales per inch (WPI) = 37, stitch length = 2.75 mm. Following table 1 depicts the color co-ordinates of the fabric that used for this research work.
2.1.2. Dyes & Chemicals Banana floral Stem (Musa sapientum), which collected from Santosh, Tangail-1902, Bangladesh was used as natural dye. ISO Standard Soap, James heal, England had used for removing the unfixed dye from the surface of colored sample.
2.2.1. Sampling Samples dyed for 20, 30, 40, 50, 60 and 70 minutes were identified as A, B, C, D, E and F respectively.
2.2.2. Natural Dye Extraction Banana (Musa sapientum) floral stems were separated from banana tree and washed. Fresh floral stem of the banana was cut into one meter pieces using cutlass. Then the pieces were sliced. Sap extracted from floral stem by roller squeezer machine. Sap was filtrated by a nylon strainer and stored in plastic container. The saps were kept in a cool place and were prevented from sun rays to avoid evaporation and possible reaction for photo-catalytic degradation.
2.2.3. Dyeing Dyeing had carried out according to exhaust method by Infra-red lab sample dyeing machine (XIAMEN RAPID, China) at 1000 for 20, 30, 40, 50, 60 and 70 minutes respectively. Then the dye bath was cooled at 400. Samples were washed at room temperature and air dried in flat dryer machine (MESDAN, Italy).Then soaping was performed for removing unfixed dye from the fabric surface by 0.5 g/L ISO standard soap at 800 for 10 minutes. For both dyeing and soaping, the material to liquor ration had kept 1:20.
2.2.4. Determination of Color Coordinates Value The color coordinates of the dyed samples were determined based on the CIE Lab system via dual beam reflectance Data-color spectrophotometer, Spectroflash SF 650X, (Datacolor, USA) keeping the following setting: Illuminant D65, Medium area view, Specular included and CIE 1964 supple-mental standard observer (10° observer). Each sample was folded twice to give an opaque view with four plies and the color coordinates value was measured automatically.
2.2.5. Determination of Degree of Color Levelness Each dyed sample were measured using Data color spectrophotometer as above specified setting considering the reading-1 as standard and other nines as sample batches. Data for each batch are analyzed with respect to color difference, ΔE value. ΔE is a single value that takes into account the differences between the L*, a* and b* values of the sample and standard in the CIE L*a*b* color system.
2.2.7. Determination of Brightness Index Brightness index was measured as per the standard (ISO-2470-1977) method using following relationship (Eq. 3) after measuring the reflectance value of the corresponding sample by Data color spectrophotometer according to above specified setting only specular excluded was set. Each sample was folded twice to give an opaque view with four plies and the reflectance value was measured automatically.
Brightness index= Reflectance value of the substrate at 360 nm/ Reflectance value of white diffuser or white tile at 360 nm.
2.2.8. Determination of Color Fastness Standard methods were employed to evaluate various color fastness properties of the selected dyed fabric. Color fastness to wash, rubbing (dry and wet), light, water, perspiration was accessed by using grey scale of color change and staining according to ISO 105-C06:2010, ISO-105x12:1995, EN ISO 105-E01:2013, ISO 105-E04:2013 and EN ISO 105-B02: 2013 correspondingly.