Research On Structure And Performance Of Ultrafine Fiber Composite Air Filter Media

At present,ultrafine glass fiber has been widely applied in the high efficiency air filter medium.But the strength of the medium is poor.Fibrillated lyocell fiber is smaller in diameter and larger in specific surface area than glass wool fiber.And fibrillated lyocell fibers are intertwined with each other.So they can make the filter medium have good strength,high filtration efficiency as well as high filtration resistance.For air filter media,single fiber or single-layer structure cannot meet its application.Therefore,in this study,glass wool fibers and fibrillated lyocell fibers were used as the raw materials to prepare double-layer composite air filter medium.The structure and performance characteristics of the medium have been explored.In this paper,five kinds of glass wool fibers and five kinds of fibrillated lyocell fibers with different diameters were used as the raw materials and they were deposited over PET nonwoven to prepare the double-layer filter medium by the wet-laid process.Moreover,in order to explore the influence of capillary adhesion between fibers on the structure and performance of the filter medium,the composite filter medium with mixed ultrafine fibers were dried by heating and freeze drying.The specific content and main conclusions are as follows:1.The beating degree is a general concept.And there is no corresponding relationship between the beating degree and the average diameter of the fiber.So it is not suitable to characterize the diameter of ten kinds of ultrafine fibers used in this paper.Specific surface area is suitable to characterize fibrillated lyocell fibers in this paper.The software Diameter J which runs as plugin in Image J is able to measure fibers in SEM images,it is suitable to characterize glass wool fibers in this paper.2.The strength of the single-layer filter medium(40 g/m~2)prepared by glass wool fibers is poor,while the filtration resistance of single-layer filter medium(40 g/m~2)prepared by fibrillated lyocell fibers is too high.Although mixing the two can improve the strength and reduce the filtration resistance of the filter medium to a certain extent,the resistance of the filter medium is still large.Therefore,in order to further reduce the resistance of the filter medium,the subsequent research adopted the method of preparing the double-layer filter medium by depositing 4 g/m~2 ultrafine fiber layer on the surface of the PET nonwoven.3.As the diameter of the fiber decreases,the resistance as well as filtration efficiency of double-layer filter medium increase,while the air permeability,the porosity,the thickness and the mean pore size decreases.The variation trend of the double-layer filter medium is similar whether they are prepared by glass wool fiber and PET nonwoven,or by fibrillated lyocell fiber and PET nonwoven.However,the double-layer filter medium prepared by fibrillated lyocell fibers have lower porosity and higher resistance.When the efficiency is close,the resistance of the filter medium prepared by fibrillated lyocell fiber is larger,so glass wool fiber has better filtration performance than fibrillated lyocell fiber.4.The double-layer composite filter medium are prepared by mixed TS5 and BLM5 in different proportions.And the filter medium are dried by heating and freeze drying in order to explore the influence of capillary adhesion between fibers on the structure and performance of the filter medium.Compared with the heated filter medium,when the ratio of TS5 and BLM5 is 2:8,4:6,6:4,8:2,respectively,the efficiency of freeze-dried filter medium is increased by3.5%,5.5%,9.8% and 12.2%,respectively;the resistance is reduced by 20.4%,28.1%,23.3%and 33.2%,respectively.The freeze-dried filter medium have higher efficiency and lower resistance than the heated filter medium.Compared with heating,freeze drying can make the double-layer filter medium prepared by mixed ultrafine fibers obtain better filtration performance.