Investigation On Melt Differential Electrospinning Of Polymer Melt Based On Shear Thinning

Polymer melt electrospinning technology has green preparation process.It is one of the important technologies for mass production of polymer micro/nano fibers and has great development potential.However,in the process of polymer melt electrospinning,problems such as high melt viscosity,poor spinning effect and coarse fiber diameter are often faced.Researchers often increase the spinning temperature or add materials to reduce viscosity,but if the temperature is too high,it will cause the polymer to decompose,adding materials may affect the original characteristics of the material,and increase the manufacturing cost and difficulty.Therefore,a new methods to expand the types of spinnable materials,improve the spinning effect of polymers,and reduce the fiber diameter is of great significance for the preparation of polymer micro/nano fibers by melt electrospinning.This paper first summarizes the methods and challenges faced by melt electrospinning to prepare polymer micro-nano fibers,and analyzes in detail the method of changing the viscosity of materials in polymer electrospinning.Based on the shear thinning theory of polymer and the Couette flow model,based on the original melt differential electrospinning device in our laboratory,a melt differential electrospinning method based on the shear thinning principle is proposed and designed a melt differential electrospinning device based on shear thinning,and the shearing force is generated by introducing a rotating shaft to make the polymer shear thinning.The melting of the device is simulated and analyzed by Modex 3D and finite element analysis software.The volume filling process and electric field distribution verify its rationality.Then,the degradable material polylactic acid(PLA)with shear thinning characteristics was used to determine the appropriate feeding speed.The experiment explored the influence of different central axis shear speed on the number of jets,fiber diameter and their distribution.The outcomes indicate that with the shearing speed increase,due to the influence of centrifugal force disturbance,the number of jets at the tip of the differential nozzle will reduce,but it can effectively reduce the fiber diameter and improve the uniformity of fiber distribution.In particular,when the shear speed is 50 r/min,the fiber diameter decreases from 3.23?m at 0 r/min to 860 nm at 50 r/min,and the standard deviation of fiber distribution decreases from 0.62 ?m to 0.28 ?m.The effect is close to the fineness of PLA fiber modified by adding plasticizer.Preliminary verification of the feasibility of the device using the principle of material shear thinning to improve the spinning effect and reduce the fiber diameter.Finally,special engineering plastic polyphenylene sulfide(PPS)was selected to research the influence of different shear speeds on the diameter,crystallization performance and thermal stability of PPS fibers.The results indicate that with the shear speed within a certain range increase,the diameter of the PPS fiber can effectively reduce,and contribute to enhance fiber performance,which is good for improving the sustainability of PPS fiber products in the high temperature environment.If the shearing rotation speed is too high,it may reduce the crystallinity of the fiber and deteriorate the mechanical properties.Secondly,the effects of adding different proportions of hyperbranched polyester(HBP)on the morphology and fiber diameter of PPS fibers are studied.The results show that when HBP is not added,the average fiber diameter is 5.91 ?m,when the HBP addition ratio is 0.25%and 0.5%,the average fiber diameter decreases to 2.55 ?m and 2.61 ?m,respectively.However,as the addition ratio increases,the fiber diameter increases again,and the surface of the fiber membrane is burnt yellow.When the addition ratio is 4%,too much dripping prevents the formation of fibers.Finally,the PPS fibers prepared by the above two processes are compared with the commercial PPS fibers from Zhejiang NHU Co Ltd.The result shows that the average diameter of PPS fibers prepared by using melt differential electrospinning device based on shear thinning at a shear speed of 100 r/min is 2.58 ?m.Compared with the PPS fibers prepared by adding HBP,the average diameter is close,but the standard deviation is smaller,and the fiber morphology quality is significantly better.Compared with commercial PPS fibers,the fiber morphology quality is equivalent,but the fiber diameter is much smaller than the commercial PPS fiber which average diameter is 14.59 ?m.In summary,this paper proposes a new method of melt differential electrospinning based on the principle of shear thinning,and designs a melt differential electrospinning equipment based on shear thinning.PLA and PPS are chosen to study the effect of increasing rotational shear on the spinning process,fiber diameter and performance.The research in this paper provides a new method for expanding the types of spinnable materials in melt electrospinning and reducing the viscosity of spinning materials.It has certain reference significance for improving the spinning effect of melt electrospinning polymers and reducing the fiber diameter.