Preparation And Properties Of Polyimide Fiber By Dry Centrifugal Spinning Controllably

Polyimide（PI）fiber is one of the most promising high performance fibers in the 21st century,which exhibits outstanding thermal,mechanical and dielectric properties due to the rigid aromatic heterocyclic structure in its molecular backbone,and has broad application prospects in the fields of aerospace,electronic packaging and building protection.In recent years,with the continuous development of synthetic monomers,processing processes and modification methods,the research of PI fibers has made great progress,and also promoted the breakthrough of its large-scale production and innovation in application development.In this paper,a two-step method for the preparation of polyimide fibers using planar collected centrifugal spinning was presented.Poly（amic acid）（PAA）solution was used as the raw material to prepare polyimide fiber mats,which were then thermally imidized to prepare polyimide fibers,and the effects of different process parameters on the microscopic morphology and structure of the fibers were investigated.Based on the excellent dielectric properties and high temperature resistance of PI fibers,combined with the dense three-dimensional network structure obtained by centrifugal spinning,the insulating properties of PI fiber paper and the antibacterial filtration properties of polyimide/silver（PI/Ag）fiber mats obtained by Ion-exchange self-metallization were further investigated.The main contents of the full paper are as follows.（1）The PAA fibers were fabricated by planar collected centrifugal spinning method,and then PI fibers were fabricated by thermal imidization.The effects of spinning speed,spinneret aperture and collection height on the microscopic morphology of PAA fibers were investigated.The results showed that in the studied range,the higher the rotational speed,the smaller the fiber diameter and the decrease of multifilament;the smaller the diameter of the spinneret aperture,the smaller the fiber diameter and the increase of multifilament;the higher the collection height,the smaller the fiber diameter and the decrease of multifilament.The velocity and motion time of jet flow during the spinning process were studied by constructing centrifugal spinning motion model.In addition,the effect of different imidization temperatures on the fiber structure was investigated by adjusting the imidization temperature,and the results showed that the highest degree of imidization was obtained by heat treatment at 320°C.（2）Different PI fiber paper are prepared by using the planar collecting centrifugal spinning method,followed hot pressing and hot imidization,by adjusting the spinning process parameters,and the PI composite paper with“sandwich”structure was prepared by hot pressing the PAA fiber mats with two layers of PAA film.The results show that PI fiber paper has high thermal stability and mechanical properties.The dielectric constants of all PI fiber paper were in the range of 0.78～0.95 in the frequency range of 10²～10⁶ Hz,and the surface static voltage of PI fiber paper had a large effect on their dielectric constants.In addition,PI-FP-4 exhibited the highest breakdown strength of 8.22 k V/mm,and PI-CP-4 exhibited 145.66%higher breakdown strength than PI-FP-4,reaching 20.18 k V/mm,which was 41.04%of PI-Film.（3）The PI/Ag fiber mats were fabricated by using the planar collected centrifugal spinning method,followed hot pressing,silver ion exchanging and hot imidization.The results showed that the PI/Ag fiber mats exhibited excellent thermal stability,and the tensile strength and Young’s modulus of PI/Ag-180 reached 1.76 MPa and 20.03 MPa,respectively.Due to the porous network structure and super surface static voltage,PI/Ag fiber mats realized the simultaneous operation of both mechanical filtration and electrostatic adsorption capture mechanisms.Among them,the filtration efficiency of PI/Ag-260 for PM_0.3 was 99.09%,and the air resistance was 103.67 Pa.In addition,using the inhibition circle method,it was observed that the inhibition circle diameter of PI/Ag fiber mats was about 12 mm against E.coil,and about 13 mm against S.aureus,showing antibacterial performance.