Abstract:

Significance The development of high-performance yarn materials is a focal point of research in textile engineering and materials science. Electrospun nanofibers possess high specific surface area, porosity, unique interfacial properties, and rich physicochemical properties, and the aggregation of these fibers into yarns is an important approach to developing high-performance yarn materials. In addition, the yarns with anisotropic structural properties allow them to be made into 2-D or 3-D products using weaving or knitting technology. The versatile product structure and ease of functionalization make electrospun nanofiber yarns exhibit excellent properties in fields such as tissue engineering, moisture and heat management, energy sensing, and defense industry applications. However, current electrospinning techniques face challenges in low preparation efficiency and weak mechanical properties, which require further breakthroughs.

Progress In this paper, the forming methods of electrospun yarns from the principle of fiber aggregation and twisting are firstly reviewed, and the representative techniques are summarized. These yarn forming methods can be divided into manual twisting, electricity inducement, water bathing, high speed rotation and airflow coordination. At present, the fiber collector rotary twisting is the most commonly used method for electrospun yarn preparation, which has the advantages of good fiber orientation, yarn uniformity and stable yarn formation process. Subsequently, the influence factors affecting the yield of electrospun nanofiber yarns are discussed and summarized. The yarn yield is affected by the fiber yield, molding method, and material properties and other aspects. As the fiber yield increases, the yarn yield also increases significantly. The combination of four-nozzle needleless electrospun technology and yarn forming technology increases the yarn yield by 5 m/min, but it is still much smaller than that of the conventional spinning method. Finally, the effects of process, device and material on the mechanical properties of yarns were investigated from the perspective of yarn microstructure and fiber properties and are summarized. Moderate twist, high fiber orientation and high fiber crystallinity are all conducive to the yarn strength. At present, the polyacrylonitrile (PAN) electrospun yarns treated by hot drafting and bifunctional poly (ethylene glycol) bisazide (PEG-BA) modification are shown to have the most attractive mechanical properties. The yarn strength reached 1 236 MPa with the tenacity of 118 J/cm³, which initially reached the level of spider silk.

Conclusion and prospect The paper systematically reviews the preparation method, influencing factors influencing yield and strength of electrospun yarns. In order to address the issues of inadequate mechanical properties electrospun nanofiber film, electrospun nanofiber yarns have been prepared using various techniques such as manual twisting, electricity inducement, water bathing, high speed rotation and airflow coordination. The current technology for preparing electrospun nanofiber yarn is primarily based on a solution electrospinning system with single/double needles, resulting in low fiber yield and subsequently low yarn yield. Enhancing the yield of yarn can be achieved by combining needle-free electrospinning systems with spinning technologies, for which it is necessary to investigate the motion patterns of needle-free multi-jet electrospinning and orientation deposition twist methods. Simultaneously, developing an environmentally friendly spinning liquid system is crucial to mitigate risks posed by common organic solvents and achieve a sustainable preparation process. Melt electrospinning technology offers advantages such as complete conversion of raw materials into fibers, minimal jet whipping effects, and solvent-free preparation processes. Exploring novel approaches for enhancing the yield of melt electrospinning fiber thinning and controlling jet aggregation into yarn represents a pivotal avenue towards the sustainable production of electrospun nanofiber yarns. The reinforcement of electrostatically spun nanofiber yarns necessitates a harmonious integration of material system, device design, process control, and post-processing techniques to optimize yarn orientation and mechanical properties at the single fiber level. Investigating the spatial dynamics of electrospun fibers and evolving characteristics of the spinning jet during the fabrication process emerges as an indispensable means to enhance both yarn alignment and tensile strength. Furthermore, implementing post-treatments effectively enhances yarn structure and individual fiber strength, thereby significantly improving overall mechanical performance.

Key words: electrospinning, nanofiber yarn, yarn preparation technology, mechanical property, yarn yield