Application Cases

Experiment Name: Preparation of PVDF via Electrospinning Process

Research Focus:
In recent years, electrospinning technology has gained significant attention in the field of materials science and technology worldwide, becoming the preferred method for producing continuous nanofibers. Polyvinylidene fluoride (PVDF), a white or translucent powdered crystalline polymer with fluorinated semi-crystalline thermoplastic properties, is an ideal material for membrane separation and oil-water separation, as well as a hydrophobic material with excellent water repellency. The preparation of PVDF films using electrospinning technology offers advantages such as low cost, ease of operation, and high efficiency. The resulting PVDF and its composite nanofiber membranes have broad application prospects in wearable devices, sensors, biomedicine, electrical engineering, and environmental protection in construction.

Currently, there is relatively limited research on the process parameters for preparing PVDF films via electrospinning. Therefore, this study investigates the effects of two key parameters—spinning voltage and spinning speed—on PVDF films. Scanning electron microscopy (SEM) and water contact angle measurements were used to analyze PVDF films prepared under different parameters, exploring the influence of voltage and speed adjustments on the microscopic morphology and hydrophobicity of PVDF fiber membranes. By comparing experimental data, the optimal combination of spinning voltage and speed for preparing PVDF films via electrospinning was determined, providing a theoretical reference for the subsequent preparation of PVDF composite membranes.

Experimental Objective:
To prepare PVDF films using electrospinning, regulate spinning voltage and spinning speed, and study the effects of these two key parameters on PVDF films.

Test Equipment:
High-voltage amplifier, signal generator, oscilloscope, cold-field emission scanning electron microscope, electric blast drying oven, syringe pump, syringe, etc.

Experimental Process:
The signal generator produces an excitation signal that is input into the high-voltage amplifier. The high-voltage amplifier amplifies the input signal, and the amplified voltage is output to the syringe and the conductive substrate, respectively, creating an electric field between the syringe and the conductive substrate due to the high voltage. During the electrospinning process, the ejection device is filled with a charged polymer solution or melt. Under the external electric field, the polymer droplets held at the nozzle by surface tension accumulate charges on their surface under the electric field induction, experiencing an electric force opposite to the direction of surface tension. As the electric field gradually strengthens, the droplets at the nozzle are stretched from spherical to conical, forming the so-called Taylor cone. When the electric field strength increases to a critical value, the electric force overcomes the liquid's surface tension, ejecting from the Taylor cone. The jet oscillates and becomes unstable under the high electric field, undergoing irregular spiral motion at extremely high frequencies. During high-speed oscillation, the jet is rapidly stretched thin, and the solvent quickly volatilizes, ultimately forming fibers with diameters at the nanoscale, which are randomly dispersed on the collection device, forming a non-woven fabric. The experimental block diagram is shown in Figure 1-1.

Figure 1-1: Experimental Block Diagram of PVDF Preparation via Electrospinning Process

Experimental Results:

Figure 2-1: SEM Images of PVDF Fiber Membranes under Different Spinning Voltages [(a) 10kV; (b) 12kV; (c) 15kV; (d) 18kV; (e) 20kV]

As shown in Figure 2-1, the spinning solution can be effectively stretched to form fibers under different voltages, but the microscopic morphology and fiber diameter uniformity of each fiber membrane vary. Particularly at 10kV, fiber breakage occurs, and the diameter is relatively large. This is because, under low electric field strength, the surface tension of the spinning solution dominates, and the electric field strength is insufficient to overcome the surface tension of the spinning solution, making the formed fibers less likely to be stretched and split, and molecular chains prone to breakage, resulting in thicker nanofiber diameters. However, when the spinning voltage gradually increases to 12k–15kV, the electric field strength gradually enhances, making the spinning solution jet more easily stretched and split, thereby generating nanofibers that are finer, continuous, and have a smooth surface. As the spinning voltage further increases to 18kV or even 20kV, the excessive electric field strength increases the flow rate and speed of the spinning solution jet. This leads to insufficient fiber splitting during the jet process, resulting in bead-on-string nanofibers, increased variability in fiber diameter, and even the production of thick fibers with diameters up to 1000nm.

Recommended High-Voltage Amplifier: ATA-7100

Figure: ATA-7100 High-Voltage Amplifier Specifications

This document has been compiled by Aigtek. For more application cases and detailed product information, please stay tuned. Xi'an Aigtek Electronics has become a large-scale instrument and equipment supplier with an extensive product line in the industry. Demo units are available for free trial.