Preparation Of Multi-dimentional Pore Structure Of Acetate Cellulose Fibrous Composite Filter Material And Studies On Its Structure And Performance

The air quality is deteriorating with the rapid development of industry.The continuous haze weather causes many emerging problems on people's health and living quality.The filter materials with superior performance are needed in order to get clear air.Fibrous filtering materials play an important role in the filter materials due to its large specific surface area and high porosity.The surface state and pore structures of fibrous filter materials are important effects for the fibrous filter materials performance.And the porous fibers have the lager specific area and the surface roughness,which are benefit to the adsorption of the filter materials.Therefore,there is a great significance of using porous fibers in the preparation of high efficiency and low resistance filtering material field.In this study,with the help of a high volatile solvent system,multi-dimension porous structure composite filter materials is prepared with cellulose acetate(CA)as raw material,organic montmorillonite(O-MMT)as additive,polyester melt-blown nonwoven fabric as base cloth.The main research contents include the following aspects.(1)Preparation of porous acetate cellulose fibers.The morphologies of fibers were controlled by changing the solution properties(solution concentration,ratio of solvent)and spinning process(spinning voltage,spinning speed,spinning distance).The results showed that,the solution properties played an important role in the morphology of porous fiber's morphology.The morphology was transformed from “porous particle” to “ribbon-like fibers”,finally to “cylindrical fibers” and the diameter of fibers was decreased with the decreasing of methylene chloride(DCM)ratio in the condition of the solution concentration 5wt%,spinning voltage18 kV,spinning speed 1mL/h,spinning distance 12 cm.With increasing of cellulose acetate concentration,the morphology was transformed from “porous particle” to “ribbon-like fibers”,and finally to “cylindrical fibers” in the condition of DCM/acetone 8:2,spinning voltage18 kV,spinning speed 1m L/h,spinning distance 12 cm.and the impact of spinning technology on fiber morphology mainly in the change of fiber diameter.The increase of spinning voltage,the decrease of spinning speed and proper receiving distance,were helpful to reduce the diameter of the fiber.(2)Preparation of CA/O-MMT composite membrane with porous fibers.Using spinning technology,preparation CA/O-MMT composite porous fibers with intercalating the CA molecular chain into the interlayer of montmorillonite by mechanical stirring method.The FTIR?TEM?SEM and mechanical tensile test were used to study the effects of O-MMT for composite fiber morphology and performance.The results showed that,the CA and O-MMT were combined by physical way.The arranged layer structures would be found when 2wt.% O-MMT was added.The agglomeration of O-MMT would happen and the bead would appear when 4wt.% O-MMT was added.The O-MMT could decrease the elongation at break of the membranes and improve the tensile strength,the tensile strength would be the best when 3wt.% O-MMT was added.(3)Filter performance of multi-dimensional porous composite filtering materials.The multi-dimensional porous composite filtering materials was prepared by combining the electrospun cellulose acetate fibers with PET nonwoven fibers.And then,the filtration performance with different morphologies of eletrospun fibers,different spinning times,different air flow and different intercrossed structures were studied.In order to combine the advantages of nanofibers and porous fibers and improve the filtration efficiency of filters,the cross structures of porous fibers/nanofibers composite filters were made,and the effects of cross structures to filter performances were studied.The result shows that,the morphology of “ribbon-like” fiber could improve the filtration efficience,and the morphology of “particle-like” fiber was benefit the decreasing of pressure drop.With the increasing of spinning time,the filtration efficiency and pressure drop of the filter materials were both increased.With the increasing of air flow,the filtration efficiency of the filter materials decreased slightly,but the pressure drop of the filter materials decreased obviously.With the increasing ratio of the nonporous fibers in the composite membranes,the pore distribution was decreased,the pore size was decreased,the packing density was increased,and the filtration efficiency and pressure drop of the filter material both increased.When the spinning needle number ratio of porous fiber to nonporous number was 1:2,the prepared composite membranes possess the best qulity factor.And when the air flow was 80L/min,the pressure drop was only 315 Pa,and the filtration efficiency was 99.999%.