Synthesis, Characterization and Dyeing Performance of Novel Naphthalimide-Based Monoazo Acid Dyes on Nylon 6.6 Fabrics

Abstract

Four new monoazo acid dyes were synthesized on the basis of 1,8-naphthalimide core with H-acid, gamma-acid, J-acid and R-acid as coupling components. FTIR, UV-Vis and mass spectrometry verified their structures. Nylon 6.6 was dyed by the exhaust method, and the fastness was determined according to AATCC standards. The dyes exhibited considerable absorption in the visible region (λmax = 515 - 546 nm) with molar extinction coefficients at about 0.89 x 104 to 11.1 x 104 L·mol-1·cm-1. Wash fastness was rated 3-5, perspiration fastness 3-5, light fastness 4-7, and exhaustion was up to 94%. Colorimetric data showed color tunability from violet-purple to pink-magenta, with a chroma index of up to 37, revealing strong color intensity and stability. These findings indicate that the dyes possess high affinity for the fiber, good stability of shade development, and high stability under textile processing conditions. The study was confined to nylon 6.6 under laboratory conditions, and further work is needed to test its behavior on other polyamides and to assess its environmental performance. Overall, the findings substantiate the potential for naphthalimide-derived azo acid dyestuffs as a versatile class of fiber-selective colorants for synthetic textile applications.