Study On The Preparation Of Side-by-side Bicomponent Pla Nanofiber Membranes And Their Filtration Performance

Particulate pollutants floating in the air in the form of aerosols and microorganisms such as bacteria and viruses attached to the particles can enter human organs through the respiratory system,causing respiratory diseases and various derived diseases,seriously threatening people’s health.In addition,the problem of microbial contamination in water and the necessary sterilization operations in the biomedical field have contributed to the booming development of the filter fiber material and membrane material industry in the past 20 years.At the same time,the scientific and engineering requirements of the field are also getting higher and higher with the progress of society.How to utilize materials with better biocompatibility and more environmental friendliness（such as recyclable bio-based degradable materials）to achieve the effective removal of fine particles and microorganisms more efficiently is of great significance for the development in the medical and health field.Side-by-side bicomponent electrospinning fibers are a newly developed type of fiber membrane material,having more prominent advantages than traditional fiber filter media due to their thin diameter,large specific surface area,high porosity,adjustable pore size and unique bimodal diameter distribution.Taking full advantage of the respective performance advantages of the two component materials or having new structures and properties can optimize the overall performance of the fiber membrane to achieve the specific requirements in the application.In this paper,a novel side-by-side bicomponent nanofiber composite was prepared by using Poly（L-lactic acid）（PLLA）and Poly（D-lactic acid）（PDLA）as raw materials,introduced with Aluminum Chloride Hexahydrate（AlCl₃·6H₂O）.The surface morphology,chemical structure,crystal morphology,thermal properties,pore structure,wettability and filtration properties of the bicomponent fiber membranes before and after adding AlCl₃ were studied in detail.The research contents are as follows:（1）Using PLLA and PDLA as materials,side-by-side electrospinning experiments were carried out.By continuous adjustment of the parameters in the experiment,the effects of process parameters such as the solution concentration of PLLA and PDLA components and electrospinning voltage on the morphology of side-by-side fibers were studied.The optimal electrospinning conditions were determined to prepare a bicomponent fiber membrane sample with good morphology and a high proportion of side-by-side fibers.Characterization by SEM,FTIR,DSC,etc.,proved that the side-by-side bicomponent PLA fiber membrane with the number average ratio of 48.3%was efficiently synthesized.（2）One of the difficulties faced in the side-by-side electrospinning experiment was that the two component jets were easily separated in the electric field,because they had the same electrical charges on their surfaces,and the same properties repelled each other.Therefore,the spinning solution was improved in this experiment.By introducing AlCl₃salts into the PDLA component,according to the principle that opposite charges attracted each other and the increase of the electrical conductivity could improve the fiber morphology,the synthesis efficiency of the side-by-side fibers was further improved.The proportion of the side-by-side fibers in the s-s+AlCl₃ fiber membrane prepared in the experiment was calculated,showing that the number average statistics increased to 64.7%,and the weight average statistics increased to 86.4%.（3）The diameter of the s-s+AlCl₃ fiber membrane was bimodal distribution,and the supporting effect of the side-by-side fiber was combined with the advantages of the small diameter and small pore size structure of the single fibers,so that the fiber membrane had a good pore structure,excellent filtration performance and prominent air permeability.Under the condition of extremely low basic weight of 1.12 g/m²,the filtration efficiency and pressure drop of the prepared s-s+AlCl₃ fiber membrane reached 96.2%and 30 Pa,respectively.Besides,the QF value was as high as 0.109 Pa^-1.This fiber membrane with a unique bimodal diameter distribution structure could not only efficiently intercept small-size aerosol particles,but also significantly reduce pressure drop,improve air permeability,and have better comprehensive filtration performance,which was conducive to achieving high-efficiency filtration under the condition of low energy consumption and improving the service life.（4）The average pore size of the s-s+AlCl₃ bicomponent fiber membrane after the functional modification treatment of quaternary ammonium salt was reduced,and the surface of the membrane changed from hydrophobic to hydrophilic.Importantly,the membrane had better antibacterial performance and sterilization filtration performance.The results of antibacterial test evaluated by inhibition zone method indicated that when the concentration of the quaternary ammonium salt finishing agent was 20 g/L,the area of the inhibition zone was the largest,and the bacterial removal rate after the filtration of the original bacterial solution reached as high as 99.99%.Under the simultaneous action of pore size retention and electrostatic adsorption,the filtration efficiency of E.coli and S.aureu was so greatly improved that the excellent bacterial removal effect was achieved.This biomass-based biodegradable and green filter material has potential applications in filtration,separation,biomedicine,personal protection and other fields.