Abstract:

Objective The processing and transformation of fibers often involve complex processes, which fail to meet specific functional and performance needs. Developing direct, green, and multifunctional nanofiber materials holds significant theoretical and practical value. Additionally, dyeing-related environmental pollution remains a major challenge in textile engineering. In order to address such issues, this study focuses on producing composite nanofiber yarns with excellent mechanical and hydrophilic properties by electrospinning, while achieving multi-color yarns through dope dyeing.

Method Thermoplastic urethane/polyacrylonitrile(TPU/PAN)nanofiber yarns were prepared by electrospinning, where two oppositely charged jets neutralized and aggregated at a funnel collector under electrostatic fields, then twisted into nanofiber yarns by rotation. In order to achieve better mechanical properties of the yarn, the spinning solution ratio and spinning process were optimized. The surface morphology was observed using SEM, and the breaking strength and elongation at break were tested using an electronic single yarn strength tester. The optimal parameters were then determined. The hydrophilic properties of the blended yarn were studied using video contact angle tonometry. Cationic dye was selected to prepare multi-color nanofiber yarns, and the color fastness test was conducted by using the anti-rubbing color fastness instrument and anti-wash color fastness testing machine.

Results Optimizations of spinning liquid ratio and spinning process were the focuses of this study to achieve high mechanical properties. PAN had excellent spinnability but poor mechanical properties, while TPU provided high strength and elasticity. The high mechanical properties nanofiber was prepared from the PAN and TPU mixed spinning solution. Increasing TPU content initially improved breaking force and elongation at break, but further increases reduced spinnability, decreasing mechanical strength. By controlling the ratio of PAN to TPU at 2∶1, the resulting nanofiber yarn exhibited optimal morphology with a smooth surface, uniform structure and high mechanical strength. For the spinning process, the continuity of the yarn preparation was found to decrease when the rotation speed of the funnel collector exceeded 180 r/min and the voltage of the high voltage generator exceeded 8 kV. Compared with commercial spandex yarns and commercial acrylic yarns, the blended yarns had excellent hydrophilicity. The water contact angle is tested to be 28.5° using a video contact angle tensiometer; and the capillary rise height is determined as 18 cm through the capillary effect. After soaking, the suspension of the yarns is maintained until the dripping time dropped below 30 s and the liquid retention rate is calculated as 489.2%. Cationic dyes were added to the spinning solution for in-solution dyeing, which enabled the production of multicolored TPU/PAN yarns, then the yarns are woven into multicolored fabric using a loom. DFT calculations showed that the cyano groups(—C≡N) and amide groups(—CO—NH—) in the blended yarn have strong electrostatic adsorption with the cationic dye, leading to higher binding energy and improved color fastness of the multicolored nanofibers. The yarns showed minimal color transfer to the rubbing cloth, indicating excellent rubbing resistance. Then the color fastness of soap washing was tested. After soaping the TPU/PAN mixed fabric in soap liquid at 40 ℃ for 30 min, the color of the fabric sample did not change much, showing the color fastness was great.

Conclusion This study utilizes PAN and TPU to create oriented nanofiber yarns by electrospinning, exploring the influence of solution composition, voltage, and collection speed on yarn production. Optimal conditions are TPU to PAN ratio of 1∶2, voltage of 8 kV, and collection speed of 180 r/min, resulting in improved mechanical strength and hydrophilic properties of the blended nanofiber yarns. Cationic dyes in the spinning solution allow colored yarns with excellent colorfastness through electrospinning. Density functional theory calculations analyze polymer-dye interactions. Utilizing a loom, an array of vibrantly colored fabric samples are intricately woven,so as to enrich the function and color of nanofibers.

Key words: electrostatic spinning, polyacrylonitrile, thermoplastic polyurethane, nanofiber yarn, high specific surface area, dope dyeing, cationic dye