Preparation Of Micro-nano Graded Fibers By Centrifugal-electrostatic Spinning And Its Applications

In nature,to adapt to dynamic and changeable environments,all organisms contain diverse structures that each assume different roles.The multilevel hierarchy structure is valuable and essential in the course of evolution.Materials with a single structure have been prepared easily in previous studies;however,it is difficult for this sort of material to achieve the various functions or performance that is required in practical applications.For example,nanofibers,which are of intense global interest,are used widely in fine-particle filters,Li-batteries,sensors,wound dressings,bioengineering,tissue engineering,reinforcements,characterization6 and other fields,because their small diameter can yield a small pore size,high porosity,excellent connectivity,large specific surface area and other excellent performance in various materials.However,these lower mechanical properties hinder the further integration of nanofibers into practical large-scale applications and limits their application to broader fields.Therefore,the preparation of fibers with a multilevel hierarchy requires further attention.At present,the commonly used methods for preparing nanofibers include electrospinning,island bicomponent composite spinning,molecular plate spinning,centrifugal spinning,centrifugal-electrostatic spinning and so on.Among them,electrospinning is the most commonly used method,but the problem of low yield and the preparation of a complex system need further improvement.While,The spinning process of island bicomponent composite spinning is complicated,and the molecular plate spinning requires higher accuracy on equipments.The developed and tested centrifugal spinning has been widely used in the construction of nanofibers due to the higher spinning efficiency than other traditional spinning methods.However,the diameter of prepared fibers mostly was micron size,and the problem of collecting fibers has not been well solved.The emergence of centrifugal-electrostatic spinning has effectively solved the problem of fiber collection in centrifugal spinning.And the fiber produced by centrifugal force and electrostatic force with smaller diameter when compared with centrifugal spinning.But,relatively few studies have focused on simultaneous diverse-material spinning,especially for fibers with different diameters at the same time.Therefore,bicomponent centrifugal-electrostatic spinning was used to construct interpenetrating-syncretic micro-nano graded fibers.In the previous exploratory studies,we found that the formation of the structure was mainly due to the different spinning solutions and the volatilization rate of the solvent.The effects of different spinning needle combinations and spinning methods on the morphology and filtration properties of fibers was studied,and we find that the same spinning needle combined with different spinning needle affected the diameter of fibers,especially for micron fibers,the diameter of fibers varies greatly.Furthermore,the diameter of fibers does not always increase with the inner diameter of spinning needles.At the same time,the existence of microfibers makes the channel inside the fiber material not only longer,but also more complex.Therefore,we first use polyester mesh as the substrate the filter material.At the same time,the sample prepared with polyester gauze as the substrate also has the interpenetrating-syncretic micro-nano graded structure.The results of filtration performance,long-term recycling filtration performance,optical transparency and impact resistant performances testes show that the structure is conducive to improving filtration efficiency and reducing pressure.And the performance of the sample has a good stability,transmittance and impact resistance.In addition,the spinning method is not limited to a base material and spinning solution,which shows that this method has a good universality.In order to further broaden the application of the above-mentioned fibers,we take into account the increasingly prominent environmental pollution problems,the research direction of our laboratory,and the background of nanofibers as catalyst carriers.The catalytic fibers were prepared by spraying method.The effects of different silica sol concentration and catalyst concentration on the morphology of materials and the photocatalytic activity of samples were studied.The experimental results show that the photocatalytic fiber can effectively degrade common polar and non-polar organic pollutants,and with good recycling performance.Among them,the introduction of silica sol realized the solid combination between the fiber and catalyst to solve the problem of catalyst shedding and difficult recovery of powdered catalyst.This method is simple and controllable.It can also be used in other supporters or catalysts,and can be effectively applied in the preparation of other catalytic materials.