Trichromatic Dyeing of Polyimide Fiber Using Its Inherent Color as a Yellow Component

Polyimide (PI) fiber is one kind of high-performance fibers with outstanding thermal stability, mechanical properties, and chemical resistance, but it is difficult to be dyed due to its tightly packed macromolecules and lack of functional groups for dyeing. Especially, the inherent yellow shade of PI fiber limits the color gamut that can be matched by trichromatic dyeing. In this study, it is proposed to investigate the possibility to dye PI fibers into a black shade with disperse dyes and basic dyes with the assistance of swelling agents. The dyeing experiments showed that, among the proposed swelling agents, N-methyformanilide (MFA) was the preferred candidate for enhancing the dyeing ability of PI fibers. Using the inherent yellow color of PI fiber as a yellow component in trichromatic dyeing it could be dyed into a black shade with good colorfastness to washing, rubbing, and dry-heating. In spite of causing a slight decrease in tensile strength the dyeing would not impair the thermal stability of PI fibers.