Electrospinning technology is one of the effective methods to prepare nanofibers. There are many influencing factors and the process is difficult to control. So what are the factors that affect the electrospinning of nanofibers?
Spinning temperature has many influences on electrospinning. Elevated temperature is conducive to the volatilization of solvents, so that the jet rapidly solidifies in the electric field, so that the diameter of nanofibers increases. On the other hand, spinning temperature changes will directly affect spinning. The viscosity, surface tension and conductivity of the silk liquid, such as increasing the spinning temperature, the viscosity and surface tension of the spinning liquid are reduced, the conductivity is increased, and the movement speed of the molecular chain of the jet is accelerated. Under the action of the electric field force, the jet increased instability, easy to form beads.
The effect of humidity on electrospinning is mainly reflected in the fact that the humidity will change the volatility of the solvent. When the humidity increases, the volatilization rate of the solvent will decrease, and the decrease of the humidity will increase the volatilization rate of the solvent. Therefore, the obtained nanometer can be adjusted by adjusting the humidity of the environment. Fiber morphology is regulated.
When the applied voltages are different, in order to break the balance between the surface tension and the electric field force, the droplets at the tip of the capillary will have different surface shapes, affecting the distribution of the droplet size and the size of the droplets that are then produced, the fiber morphology and the amount of current conducted.
Spinning fluid properties - including the molecular weight of the spinning solution, concentration, viscosity, electrical conductivity, surface tension, specific heat, phase change heat, etc.
Production conditions - including applied electric field strength, voltage spinning speed, collection distance between the spinneret and collecting plate, spinning temperature, capillary diameter, etc.
Environmental parameters - including room temperature, humidity, ambient air velocity, etc.
The viscosity of the spinning solution directly affects the morphology and properties of the nanofibers obtained by electrospinning. The higher the viscosity of the spinning solution, the more tangled the polymer molecular chains, the more unstable the jet, and the more difficult to spin. It is not easy to obtain nanofibers with uniform diameter distribution, but the viscosity is too low to form jets and only droplets can be formed.
In the electrospinning process, the spinning solution generates a jet due to the electrostatic repulsion of the surface charge, and is stretched and cured to form a film under the action of the electric field force. Therefore, the conductivity of the spinning solution has a direct influence on the spinning effect. The choice of a highly conductive solvent is the simplest direct method, or the conductivity of the spinning solution can be increased by adding inorganic salts, organic salts, ionic liquids, and conductive metal particles to the spinning solution.
In the electrospinning process, the spinning solution will form a jet when the electrostatic repulsion is greater than the surface tension of the solution. The surface tension of spinning solution not only affects the formation of Taylor cone, but also affects the movement and splitting of the jet in the high pressure field, which has a decisive effect on the morphology of the fiber. The surface tension has the effect of reducing the surface area of the liquid, so that the spinning fluid jet becomes spherical, and the electric field force in the high voltage electric field and the viscoelastic force of the spinning liquid will inhibit the rapid change of the jet shape, thereby contributing to the formation of a smooth and uniform fiber.
The receiving distance directly affects the strength of the electric field and the flight and stretching time of the jet in the electric field. When the receiving distance is small, the electric field strength will increase, and the stretching effect of the electric field force on the jet will increase, which is favorable for the formation of nanofibers with smaller diameters, but at the same time it will also reduce the jet stretching time, resulting in incomplete evaporation of the solvent. It is difficult to prepare nanofibers of uniform diameter.
If the jetting speed of the spinning solution is very small, a Taylor cone cannot be formed at the spinning port, and electrospinning cannot be performed. As the spinning liquid jet speed increases to an optimum value, the Taylor cone will continue to rotate until it is received on the receiving plate. The interval between the spraying process can fully evaporate the solvent and produce a smaller diameter and even distribution. Nanofibers; when the spinning liquid jet velocity is too high, the solvent content inside the jet increases so that it cannot be completely volatilized, the residual solvent binds the fibers, and the fibers have many beads.