Fabrication And Characterization Of Aramid Nanofiber/meltblown Nonwoven Composites For Air Filtration

Nanofibers show small diameter and large specific surface area.The nanofiber film has the characteristics of small pore size and high porosity,so it is widely used in the field of air filtration.In this paper,the micrometer Kevlar fibers were prepared into nanofibers by deprotonation under different temperature conditions based on KOH/DMSO.The surface morphology of the aramid nanofibers was characterized and analyzed by means of SEM and TEM.Then the aramid nanofibers were made into aramid nanofiber films by vacuum filtration method,which were characterized and analyzed by the chemical structure,mechanical properties and thermal properties.Then the electronegative aramid nanofibers were attached in the elector melt-blown nonwovens by an automatic film coating machine,to form a composite filter materials.Then the apparent morphology,mechanical properties,thermal properties and filtration properties of the composites were tested and analyzed.Through optimizing the preparation cycle of aramid nanofibers and analyzing the performance of aramid nanofibers/melt-blown nonwoven composite filtration material,the main conclusions of this paper are as follows:(1)Under the condition of temperature from 20? to 60?,Kevlar fibers were deprotonated in KOH/DMSO system to obtain uniform and stable dark red aramid nanofiber dispersion.Here stable dispersions of uniform high-aspect-ratio aramid nanofibers(ANFs)with diameters between 6 and 28 nm were successfully obtained.With the increase of preparation temperature,the preparation period was greatly shortened,and the diameter of the nanofibers showed a trend of decrease with the increase of preparation temperature.(2)The aramid nanofiber films of different preparation temperature were prepared by vacuum filtration method,which were consistent with the macroscopic Kevlar fibers in infrared spectrum analysis and XRD analysis.This proved that the preparation temperature did not cause damage to the structure of aramid nanofibers(3)Electret treatment was used to prepare electret melt-blown nonwoven materials.Under electret parameters with electret voltage of 15 kv,electret spacing of 3cm and electret times of 5 times,the ideal electret effect could be achieved,which provided strong conditions for the coating and bonding of aramid nanofibers in the future.(4)Due to deprotonation,aramid nanofibers with a negatively charged,could be attracted by positively charged electret melt-blown nonwoven materials,which produce electrostatic attraction effect of positive and negative charges.By means of electrostatic adsorption and intermolecular force binding of aramid nanofibers,aramid nanofibers were coated on electret melt-blown nonwovens materials and formed a continuous and uniform mesh porous aramid nanofibers film on its surface to form composite filter materials.The composite filter material has good filtration,mechanical and thermal properties.(5)When the distance of scraper was 50?m,the composite filter material had sub-micron pore structure,and the filter effect was the best by comprehensive evaluation of quality factor,with filter efficiency up to 95.61% and pressure drop to 38.22 Pa.In addition,the aramid nanofiber film had good thermal properties and porous structure,which enhances its durability at high temperature.In conclusion,this paper optimized the preparation technology of aramid nanofiber,and further coated it on nonwoven materials to form composite filter material.Compared with ordinary meltblown filter material,the mechanical,filtration and thermal insulation properties of the composite filter material were significantly improved.