The textile industry has been exploring sustainable chemicals and natural alternatives to replace harmful and carcinogenic substances used in different stages of textile production for dyeing textiles. Natural dyes are gaining popularity, as they are environmentally friendly and less harmful. Betacyanin, a type of pigment obtained from red pitahaya, commonly known as red dragon fruit (Hylocereus polyrhizus), has peels that are available as agricultural waste and can be used to meet the demand for natural dye production. This study aimed to explore and utilize dragon fruit’s peel as a natural colorant for dyeing 100% cotton knit fabric (scoured and bleached single jersey plain knit) of 170 g/m2, which could transform a low-value material into a valuable product. However, cotton’s phenolic nature and oxidation process result in negative charges on its surface, making natural dyeing challenging. Cationization with cationic agents (ForCat NCH, a mixture of cationic polyamine and 1,3,dichlori-2-propanol) and mordanting (potassium alum or potassium aluminum sulfate) were carried to improve dye exhaustion and enhance colorfastness properties. Spectrophotometer 800 was used to measure color strength (K/S), and several fastness tests, including wash, perspiration, and rubbing were conducted to assess the final product’s performance. The process parameters, such as temperatures, times, pH levels, and dye concentrations were varied to understand better the optimum conditions.

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Dragon Fruit (Hylocereus polyrhizus): A Green Colorant for Cotton Fabric

The application of plant dyes in the textile industry has been very limited due to their limited sources, incomplete color space, and narrow color gamut, etc. Therefore, studies of the color properties and color gamut of natural dyes and the corresponding dyeing processes are essential for completing the color space of natural dyes and their application. In this study, water extract from the bark of Phellodendron amurense (P. amurense) was used as a dye. Dyeing properties, color gamut, and color evaluation of dyed cotton fabrics were studied, and optimal dyeing conditions were obtained. The results showed that the optimal dyeing process was pre-mordanting with liquor ratio at 1:50, P. amurense dye concentration at 5.2 g/L, mordant concentration (aluminum potassium sulfate) at 5 g/L, dyeing temperature at 70 °C, dyeing time of 30 min, mordanting time of 15 min, and pH 5. Through the optimization of the dyeing process, a maximum color gamut range was obtained with lightness L* value from 74.33 to 91.23, a* value from −0.89 to 2.96, b* value from 4.62 to 34.08, chroma C* value from 5.49 to 34.09, and hue angle h° value from 57.35° to 91.57°. Colors from light yellow to dark yellow were obtained, among which 12 colors were identified according to the Pantone Matching Systems. The color fastness against soap-washing, rubbing, and sunlight on the dyed cotton fabrics all reached grade 3 level or above, further expanding the applicability of natural dyes.

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Dyeing Properties, Color Gamut, and Color Evaluation of Cotton Fabrics Dyed with Phellodendron amurense Rupr. (Amur Cork Tree Bark)

Natural dyes play an important role in sustainable dyeing processes. However, natural yellow dyes with good performance are rare. Traditional natural yellow dyes have issues, such as a narrow color range and poor light fastness. In this paper, a new natural yellow dye was extracted from a low-cost herb Geranium caespitosum L. (G. caespitosum). In addition, the dye composition was analyzed using UV-visible spectroscopy. The dyeing process of G. caespitosum dye on wool fabrics was optimized using single-factor experiments. Standard fastness tests were conducted to evaluate the sunlight, washing, and rubbing fastness of the dyed fabrics. The color characteristics and color gamut range of the dyed fabrics were evaluated. The obtained colors were compared and assessed with Pantone Matching Systems and Chinese traditional colors. The results showed that phenolic acids and flavonoids were present in the G. caespitosum dye solution as yellow dye compounds. The best dyeing process for wool fabrics was meta-mordanting. The dyed fabrics were bright yellow at 60 °C and golden yellow at 90 °C. All the obtained colors were in the yellow-red range. According to the ISO color fastness standards, wool fabrics dyed with G. caespitosum dye had good color fastness ratings, particularly sunlight fastness. Therefore, G. caespitosum dye is a promising natural yellow dye that can be used for wool fabric dyeing. It has advantages over other known natural yellow dyes and has certain application value.

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Study on Dyeing Properties and Color Characteristics of Wool Fabrics Dyed with Geranium caespitosum L. Extract—A New Natural Yellow Dye

ABSTRACT In this study, natural dyes were extracted from acer ginnala dried leaves and applied on wool fabric. The preferred mordant and post-mordant dyeing performance on wool fabric with Acer ginnala were confirmed by color strength (K/S). The influence of different factors on color characteristic value was revealed and qualitative analysis was carried out on the samples dyed by different concentration of dyeing solution and dyeing times. The experimental results showed that the application value of post-mordant dyeing of acer ginnala wool fabric was the largest. Moreover, the color characteristics values of post-mordant dyeing acer ginnala wool fabric influenced by different factors was lightness L* (14.89-59.57), purity C* (0.81-15.76), hue b* (0.03-15.74), hue a* (0.21-1.31) by order. The hue angle h° is between 92° and 339°, which gradually transits from yellow to orange to red and then to purple. A total of 19 colors were dyed, including 2 colors of Pantone, 4 colors similar to Pantone, 9 colors very different from Pantone, and 4 colors totally different from Pantone. All samples soap-washing fastness, rubbing fastness and light fastness are above grade 3, which showed a wide prospect of application.

Fei Xu

Papers

Dyeing Properties, Color Gamut, and Color Evaluation of Cotton Fabrics Dyed with Phellodendron amurense Rupr. (Amur Cork Tree Bark)

Study on Dyeing Properties and Color Characteristics of Wool Fabrics Dyed with Geranium caespitosum L. Extract—A New Natural Yellow Dye

Color Characteristics, Color Gamut Range and Color Value of Acer Ginnala Dyes on Wool Fabric