Trichromatic Dyeing of Polyimide Fiber Using Its Inherent Color as a Yellow Component
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ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)
Trichromatic Dyeing of Polyimide Fiber Using Its Inherent Color as a Yellow Component Dongyan Shao, Changhai Xu, Jinmei Du, and Hongbo Wang* Key Laboratory of Eco-textiles, Ministry of Education, College of Textiles and Clothing, Jiangnan University, Wuxi 214122, China (Received April 18, 2019; Revised September 30, 2019; Accepted December 18, 2019) Abstract: 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. Keywords: Polyimide, Trichromatic dyeing, Swelling agent, Yellow shade, Black shade
pretreatment of PI fiber with alkali can improve its dyeing ability for disperse dyes and basic dyes, which is ascribed to the fact that PI fibers acquired carboxyl and acylamino groups which are produced from hydrolysis of imide groups of PI fibers under alkaline conditions and provide PI fibers with hydrophilicity and reactivity [10-12]. Nevertheless, the alkali-pretreated PI fibers could only be dyed into light shades. Furthermore, the PI fibers undergo apparent strength loss due to alkali hydrolysis. The swelling agents are so called because they can loosen the highly crystalline fiber structure for easier penetration of dye molecules, allowing the fiber to be dyed at a lower temperature. Fiber dyeing assisted with swelling agents has been widely reported and practiced for both natural fibers and synthetic fibers since the twentieth century [13-17]. Now, various swelling agents are proposed for dyeing highperformance fibers such as aramid fiber [18-21]. Anilide, benzyl alcohol and phenoxy compounds are preferably used as swelling agents because they are often of hydrophobicity with strong polarity which provides them with intense interactions with hydrophobic fibers [20,22]. According to our latest research, the dyeing ability of PI fiber could be significantly enhanced with the help of N-methylformanilide (MFA), phenoxyisopropanol (PIP), and acetophenone (AP) when disperse dyes and basic dyes were used for dyeing [23]. In this work, the preferred candidate of swelling agents would be applied for dy
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