The Preparation And Characteristics Of Side-by-side Bicomponent Nanofiber Membranes

In recent years,composite fiber materials have attracted much attention due to their versatility.The development of high-tech such as microelectronics and aerospace requires composite fiber materials with sophisticated structure.The two-component composite fiber prepared by the side-by-side electrospinning not only can fully exert the performance advantages of each component material,but also can achieve synergistic effect by complementing,and finally improve the comprehensive performance of the synthetic fiber.Compared with traditional spinning,the electrospinning process is short and operability,the obtained fiber has a finer diameter and is easy to realize surface functionalization.In this paper,three different high polymers were used as the raw materials,and a new side-by-side bicomponent nanofibers were synthesized by using the side-by-side electrospinning technology.The spinning conditions and fiber properties were systematically studied.The results show that the obtained side-by-side fiber membranes have good performance in mechanical properties and thermal stability,and broaden the application range of bicomponent fibers.At the same time,based on the published literature,this study improves the side-by-side electrospinning device and the spinning efficiency,which provides a new idea for side-by-side electrospinning.The details of our research are as follows:1.Polyvinylidene fluoride(PVDF)and polyimide(PI)were used as electrospinning materials,and side-by-side spinning equipment was used for spinning experiments.The experimental conditions were optimized to study the effects of spinning voltage,receiving distance and solution flow rate ratio on the morphology of the side-by-side fibers.The optimum spinning conditions were determined to obtain a well-formed bicomponent fiber membrane sample.One of the difficulties in side-by-side spinning is that the two jets carry the same charge and are prone to repulsion separation.Therefore,the spinning equipment was improved in the experiment.By adding a peripheral electric field at the double spinneret,the two pairs of charged jets were formed into an inward extrusion to reduce the separation and improve the juxtaposition efficiency of the fibers.It is found that the PVDF/PI side-by-side bicomponent fiber combines the performance advantages of both PVDF and PI materials,and has good thermal stability and mechanical properties.With the increase of the heat treatment temperature,the strength of the juxtaposed fiber membrane shows a certain degree of improvement in the case of ensuring the stability of the pore structure.At 230?,itcan still maintain a good pore structure and filtration efficiency,the strength is increased to2.13 times.2.In order to further study the effect of fiber structure on properties,the same electrospun materials were used to prepare samples by four-needle cross-blending and side-by-side electrospinning,the surface morphology,thermal stability and mechanical properties of blended PVDF+PI and side-by-side PVDF/PI bicomponent fibers were analyzed.The difference between the melting points of PVDF and PI materials was used to control the heating time and temperature.The heat treatment of PVDF+PI and PVDF/PI was performed to bond some PVDF fusion reinforcing fibers and improved the overall strength of the fiber membrane.The heat-treated blended PVDF+PI and the side-by-side PVDF/PI fiber membrane were assembled into a simulated battery as a lithium battery separator.The electrochemical stability window,charge and discharge performance and cycle stability were studied.The results showed that the side-by-side PVDF/PI fiber membrane exhibits superior performance after heat treatment compared with the blended fiber PVDF+PI membrane,and is more advantageous as a lithium battery separator.3.The high-elasticity polymer material TPU was introduced into side-by-side electrospinning with PVDF and PI to prepare bicomponent spiral fibers.The effects of viscosity and volatility of electrospun solutions on the formation of spiral fibers between different polymer materials were investigated.The experimental results showed that among the three twin spinning systems,only TPU and PI can obtain spiral fibers by electrospinning.Properly increasing the volatilization rate of the spinning solution is advantageous for the generation of the spiral.When the difference between the performance of the TPU and the PI electrospinning solution is relatively large,it is not conducive to the formation of the spiral.At the same time,the spiral fiber can increase the contact angle and hydrophobic properties of the fiber membrane to a certain extent.