Abstract:

Objective In order to understand the influence of electric field variation on the structure of nanofiber core-spun yarn with skin core structure with two-needle continuous water bath, finite element analysis software ANSYS is used to simulate the change of electric field distribution in the tip spacing. The morphology, diameter distribution, porosity and other structures of nanofiber core-spun yarns with different tip spacing were analyzed. The work aims to establish a theoretical basis for the optimization of process parameters of electrospinning, and provide a reference for the preparation of nanofiber core-spun yarn.
Method The continuous preparation of nanofiber core-spun yarn was achieved by using a self-made electrospinning equipment. The nanofiber core-spun yarn with polyester filament as the core yarn and polyamide 6 nanofiber as the coating layer was prepared by two-needle continuous water bath electrospinning method, aiming to acquire special properties combining the nanofiber and traditional yarn. Through the finite element analysis software ANSYS modeling analysis and scanning electron microscope observation, the theoretical and scientific study of the impact of needle tip spacing was carried out on the electric field distribution and nanofiber core-spun yarn structure.
Results By simulating the distribution and variation of electrospinning electric field with two needles, it can be confirmed that the maximum field intensity occurs at the tip of the needle. With the increase of tip spacing, the field intensity increases first then decreases and then increases as shown in Tab. 1. When the tip spacing was set greater than 40 mm, the field intensity peak with the increase of the tip spacing and gradually rise. However, considering the restrictions on the size of the electrostatic spinning equipment, and the limitation of fiber sedimentary area, tip spacing should not be too large. The needle tip spacing of 30 mm is better according to the analysis of the Tab. 1. The diameter and morphology of nanofibers can be adjusted by altering the tip spacing. According to the electron microscopy, when the tip spacing is 20 mm, the electric field interference leads to more bonding between the nanofiber. As the tip spacing increases, the interaction between the needles decreases, the morphology of nanofibers becomes more uniform and smooth, and the diameter of nanofibers decreases, as shown in Fig. 5. When the tip spacing is 80 mm, the diameter of the nanofiber reaches the minimum value of (74.43±10.79) nm. It is learnt that two-needle electrospinning requires special attention to the tip spacing while improving the yield of nanofibers to avoid the instability of jet flow caused by too small tip spacing. When the needle tip spacing is increased from 20 mm to 60 mm, the porosity of nanofiber core-spun yarn increased from 20.27% to 44.08%, indicating that the interaction between needles weakened with the increase of tip spacing, leading to improved porosity(as shown in Fig. 7).
Conclusion The simulation results show that the maximum field intensity appears at the tip, and the field intensity peak increases first, then decreases and then increases with the increase of the tip spacing. According to the electron microscopy, with the increase of the tip spacing, the interaction between the needles decreases, which can improve the porosity of the nanofiber core-spun yarn, and the diameter of the nanofiber decreases. The structure of the nanofiber core-spun yarn conforms to the changing law of the electric field strength. The results of electric field simulation have guiding significance for the study of the structure of nanofiber core-spun yarns. Due to the problems of electric field interference and equipment limitation in the experimental results, the study of process parameters is of great significance to the electric field variation in the process of electrospinning, which provide reference for subsequent research experiments. The further optimization of equipment and fiber structure and industrial production application are expected to be further discussed in future research.

Key words: two-needle, continuous water bath, electrospinning, nanofiber core-spun yarn, electric field simulation, tip spacing, polyester, polyamide 6