| Air pollution not only poses a risk to public health,but also seriously hinders the sustainable development of society.Air filtration materials have shown great potential for application due to their ability to effectively remove particulate matter,and have attracted widespread attention.Compared with commonly used air filtration composite,fibrillated fiber air filtration composite has the advantages of environmental friendliness,low cost,short preparation cycle,and easy industrialization application,and are attracting much attention.In this thesis,the preparation of Lyocell as a raw material for the preparation of fibrillated fibers,the preparation of Lyocell fibrillated ultra-fine fibers,the preparation of Lyocell/polyester/cellulose nanofibril high-efficiency air filtration composite,and the characterization of their properties were investigated,and the Lyocell/polyester nonwoven bilayer composite were further constructed.Details of the research are as follows:(1)For the preparation of fibrillated fibers,the relationship between the size of Lyocell fibrillated fibers and the regulation of process conditions was studied by regulating the sizing method,sizing time,sizing speed,fiber concentration and other process conditions using Lyocell as the raw material.The results showed that there was a negative correlation between beating time,beating speed,fiber concentration,and the diameter of Lyocell fibrillated fibers,the mean diameter of the Lyocell fibrillated fibers gradually decreased as the beating time,beating speed,and fiber concentration increased.Without Na OH pretreatment,when the beating time increased from 3 minutes to 9minutes,the mean diameter of Lyocell fibrillated fibers decreased from 15.22μm to 7.97μm,indicating that the beating time had a significant effect on the diameter of Lyocell fibrillated fibers.When Na OH pretreatment was used,the change in diameter of Lyocell fibers showed the same trend with an even more significant decrease as the beating time increased.After using 2 wt%Na OH pretreatment,at beating speeds of 12000,24000,and36000 r/min for 9 minutes,the diameter of the Lyocell fibrillated fibers decreased from15.66μm to 8.90μm,7.49μm,and 6.02μm,respectively.The fiber concentration of Lyocell had a significant influence on its raw fiber size.The average diameter of raw fibers decreased significantly from 13.29μm to 7.87μm when the fiber concentration was increased from 0.1 wt%to 0.4 wt%.This was due to the fact that inter-fiber friction improves with increasing fiber concentration,enhancing fiber-to-fiber friction and shear forces,resulting in a significant reduction in fiber diameter.(2)The problem addressed in this research is the development of efficient air filtration composite using Lyocell/polyester/cellulose nanofibril.To achieve this,a pressurized filtering method was used to prepare the composite.Initially,a Lyocell/polyester filtration composite was constructed using Lyocell fibers and polyester fibers,and the test results showed that the filtration efficiency of the 30 g/m~2Lyocell/polyester composite was only 52.69%for solid particulate matter.However,after implanting 0.5 g/m~2 of cellulose nanofibril into the Lyocell/polyester composite,the filtration efficiency of the Lyocell/polyester/cellulose nanofibril filter composite significantly increased to 98.22%,with a pressure drop of 145.50 Pa.Although the filtration efficiency of the composite for oil-based aerosol particles(DEHS)is slightly lower than that of non-oil-based aerosol particles(Na Cl),it is still effective.With the increase of relative humidity,the filtration efficiency of air filter composite has a trend of increasing and then decreasing.When the relative humidity reaches 45%,the filtration efficiency of air filtration composite is the best,up to 98.22%,while when the relative humidity reaches 90%,the filtration efficiency of air filtration composite drops significantly to 55.03%,which may be caused by the collapse of the filter composite network.Furthermore,the filtration efficiency of the air filter composite did not change significantly with an increase in the testing time,indicating that the composite has a lasting effect on filtering PM.(3)Using Lyocell staple fibers as raw materials,a modified polyester nonwoven fabric was prepared by deposition through pressure filtration.The research results showed that as the quantitative amount of Lyocell staple fibers added to the nonwoven fabric increased from 0 to 5 g/m~2 and 10 g/m~2,the mean pore size of the prepared composite decreased from 39.26μm to 8.29μm and 5.03μm,respectively.The corresponding filtration efficiency increased from 78.82%to 92.29%and 95.95%,and the corresponding pressure drop also increased from 97 Pa to 218.5 Pa and 295.5 Pa.The nonwoven fabric increased the mechanical strength,while the Lyocell staple fibers improved the filtration performance.The prepared double-layer composite has certain application prospects in the field of high-precision filtration composite. |
PDF Full Text Request