COLOR STRENGTH AND COLOR DIFFERENCE OF COTTON AND SILK FABRICS DYED WITH EXTRACTS FROM BUTTERFLY PEA FLOWERS

Abstract

Natural dyes have always been of interest due to their non-toxicity and environmental benefits. In this work, cotton and silk fabrics were dyed with extracts from butterfly pea (BP) flowers. Accordingly, the effects of pH value, liquor ratio, dyeing concentration, temperature, exhausting time and mordanting agents on the color strength (K/S) and the color difference (∆E) of cotton and silk fabrics dyed with BP extracts were investigated. The experimental results showed that the K/S and ∆E values of dyed cotton fabrics were much higher than those of dyed silk fabrics. The research also established the most suitable conditions for dyeing cotton and silk fabrics with BP extracts as being the following: pH of 6.0, liquor ratio of 1:5, dyeing time of 60 min, at 70 °C for cotton and 60 °C for silk. Notably, four different types of mordants, including potassium aluminium sulfate (KAl(SO4)2.12.H2O), copper sulfate (CuSO4.5H2O), ferrous sulfate (FeSO4.7H2O) and tannin, were used to enhance dyeability of cotton and silk fabrics with BP extracts. There were slight differences in the ∆E values of mordanted and unmordanted samples, while the K/S values improved significantly, especially in the samples mordanted with tannins. Color fastness and color staining to washing and rubbing were also examined, indicating that treated silk fabrics achieved higher values than treated cotton fabrics.