Study on dyeability of silk fabric with anthocyanin extracted from butterfly pea flowers

Natural dyes are always noticed because of their environmentally friendly properties as well as their health protection for the wearer. In this work, anthocyanins of butterfly pea flowers were extracted by the microwave-assisted method that obtained more effectiveness compared with the conventional method. The content of anthocyanin in butterfly pea extracts and dyed silk samples were examined and clarified by high-performance liquid chromatography, Fourier-transform infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, and ultra-visible spectroscopy. The effect of the concentration of dye extract, temperature and time duration of dyeing and type of mordants used on the color strength and color difference were studied. The results obtained showed that the color strength and color difference of dyed silk samples increased with the concentration of butterfly pea extracts but decreased at temperatures higher than 70°C and for a longer time than 70 min. Moreover, the dyeability of silk fabric was more improved with the presence of metal salts such as ferrous sulfate, copper sulfate, and potassium aluminum sulfate because of their complex formation with anthocyanins and fibroin chains. Color fastness to washing on dyed silk samples according to the AATCC standard were tested to clarify more impacts of the types and concentration of mordants.