| Electrospinning is different from traditional methods which exert voltage on polymer solution to get nanofiber. It is mainly by means of high voltage electrostatic field so that got the charged polymer solution or melt. At the nozzle end it formed the cone hanging droplets, which accelerated under the force of electrostatic force. When the electric force is large enough, the droplet can overcome surface tension to formation of a thin stream, Due to solvent evaporation in the electric field, nanofibers what like non-oven mats were got in the receiver. Electrospun nanofibrous membranes with relatively high surface area and microporous structure can be applied in various potential applications such as information technology, energy, environment, biomedical, national security, etc.Currently, the diameter of electrospun fibers is generally between 100 nm and 500 nm. Only the diameter below 50 nm, the performance of nanofibers can be significantly better than normal nanofiber. However, the fibers which diameter below 50 nm cannot easily got by the current technology, which largely limits the application of nanofibers. How to reduce the fiber diameter and increase production is the biggest challenge in electrospinning. Over the past few years, there has been a rapid development in the subject area of electro-spinning/netting (ESN), which born with electrospinning. ESN provides a one-step, versatile strategy for fabricating nano-fiber/net (NFN) membranes comprising common electrospun nanofibers and two-dimensional (2D) nano-nets. Nano-nets, assembled from net-like structured nanowires with an ultrafine diameter (5-40 nm), exhibit several amazing characteristics, such as an extremely large specific surface area, high porosity and superior mechanical performance.Polyurethane (PU) is the generic name for polymers possessing a urethane bond. It has excellent toughness and flexibility, good abrasion resistance, flexed resistance, solvent resistance, and easy molding, and has the advantages of controllable performance, so in many areas it has irreplaceable applications. In addition, polyurethane fiber membrane with excellent permeability and moisture permeability, which makes in the military, high-end clothing and biomedical has a wide range of applications.Firstly, the basic theory of electrospinning was introduced, and which factors influence on the formation nano-membrane. In this topic, PU NFN membranes were one-step controllably prepared via ESN. The FE-SEM as the main analytical tools, the effect of electrostatic spinning solution system was first to be analyzed. The results show that adding 3 wt% deionized water to the 7 wt% PU/NaCl solutions, the adhesion of common fibers was increased, but the coverage of nano-net and the diameter of fibers were reduced. In addition, the different PU also can affect the nano-net structure and morphology. The higher-density PU fibers showed higher adhesion, lower nano-net coverage rate and smaller fiber diameter. The topic also discusses the effect of voltage, tip-to-collector distance, humidity, different additives on PU NFN structure and morphology.This topic systematically investigated the tensile properties, wear properties, air and moisture permeability of PU NFN membranes. It found that the structure and morphology of PU NFN membranes were the key factors affecting the tensile properties, wear properties, air and moisture permeability. |
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