Study On Preparation And Technology Of Micro-nano Fibers Based On Torsional Lamination Technology

Torsional lamination based fiber preparation technology is a micro-and nano-fiber preparation method,which uses strong shear and tensile forces inside the laminar to stretch polymer droplets to form fibers.At present,the preparation of micro and nano fibers is mostly through such methods as electrostatic spinning,meltblast and centrifugal rotation.These methods have good effect on the fiber formation of polymer with high fluidity,but for thermoplastic polymer with high viscosity,there are some problems such as low preparation efficiency,coarse fiber diameter or environmental pollution risk.Torsional lamination is characterized by high tensile and shear,which has a good effect on the processing of polymers with high viscosity.Therefore,it is necessary to explore the potential of torsional lamination technology in the preparation of micro and nano fibers.First of all,micro-nano fibers were prepared using the principle of in situ fiber formation,and the morphology,diameter,tensile strength and hydrophobicity of the fibers under different preparation conditions were studied.In view of the characteristics that the two-phase polymer must be incompatible and have good thermal stability in the co-extrusion process of single screw,the study determined to use HDPE as the target polymer and PVB soluble in ethanol as the matrix,which is convenient for later recovery and ensures green manufacturing.The influence of the viscosity ratio,the number and mass ratio of the two polymers on the fiber diameter and morphology was investigated.The results show that the larger the viscosity ratio of PVB/HDPE is,the smaller the average fiber diameter is.When the viscosity ratio is 3.4,the average fiber diameter is 1.18μm,a large number of submicron fibers appear,and the minimum fiber diameter is 268 nm.The effect of different HDPE content on fiber morphology was investigated.It was found that the smaller the HDPE content and the smaller the diameter,the better the fiber tensile shape.When the HDPE content is 5%,the average diameter reaches 850 nm,but the fiber length is small and there are a lot of short fibers.The effects of different fiber morphology on the tensile strength,elongation at break and water contact Angle of the fiber film were tested.Finally,it was determined that the tensile strength of the fiber film reached 1.256 MPa when the content of HDPE was 15%,and the elongation at break increased with the increase of HDPE content.The water contact Angle reached 133.8° when the content of HDPE was 10%.Secondly,the process of twin-extruder torsional laminated coextrusion is simulated and analyzed.Due to the different viscosion-shear stress,melting index,flow rate and pressure of different polymers,the interface migration and interface non-uniformity of the two phase molten polymer are very likely to occur in the laminated flow channel.The outlet interface of three different viscosities of PVB and PP was investigated.The results showed that the closer the viscosity was to the two-phase interface at the same temperature and shear rate,the smaller the fusion and migration were.When the viscosity is similar,the interface deviation at the middle position at the outlet is smaller relative to the position on both sides.The relationship between outlet position velocity,shear rate and viscosity is adopted.The shear rate and velocity change trend are consistent.Since the polymer melt is a non-Newtonian fluid,the viscosity is opposite to the shear rate trend.The simulation results were verified by relevant experiments,and the morphologies of polymer fibers with different extrusion positions and viscosities were explored.The results were basically consistent with the simulation results,which provided a meaningful reference for the subsequent preparation of nanofibers.Finally,the concentrator and heating plate were designed and processed for the preparation of two-phase co-extruded long fiber.The influence of different tensile ratio and different tensile speed on the morphology of the fiber was investigated.When the tensile ratio was 8 and the tensile rate was 7mm/s,the average diameter of the fiber reached the minimum 0.61μm.The average fiber diameter is smaller and the fiber length is longer than in situ fiber formation.In summary,this paper prepared micro and nano fibers based on the torsional laminated technology,and provided a new preparation method for the preparation of high viscosity thermoplastic polymer fibers.Nano fibers were prepared by the method of simulation and experiment,and the changes of fiber morphology under different conditions were explored.This study provides some new ideas for torsional lamination preparation of nanofibers.