Factors affecting nonwoven filter materials and their analysis

2022-06-15 0 By

As a filter material, it not only needs to block and absorb more small particles, but also needs a certain amount of air flow.The fiber fineness, length, crimp, surface morphology and the area density and thickness of the fiber net all affect the filtering effect of nonwovens.Fiber fineness Fiber fineness is usually expressed by the diameter and cross-sectional area of the fiber, or is determined by the quality and length of the fiber.The smaller the fiber diameter, the larger the specific surface area, the more fibers in the unit area of the filtration material, the smaller and more complex the gap between the fibers, the narrower the pore distribution, the more opportunities for particles to be captured, and the higher the filtration efficiency.Fine fiber, uniform mechanical properties, high strength.Filter material commonly used fiber size is 1.5~ 3DTEX.2 Fiber length The fiber length affects its machining performance.The longer the length, the more twists and turns of the filter channel, the more chances of particle collision and capture, the filtration performance of the material is enhanced, but the porosity is low, the filtration resistance increases.When the fiber length is too long, carding is difficult, the mesh quality is poor, the uniformity of the fiber mesh is reduced, and the filtration performance of the material is affected.At this time, the porosity of the material is large and uneven, leading to low filtration resistance 3 fiber crimp for the larger crimp of the fiber, the crimp between the fibers will be smaller and smaller.When tensile stress is applied, the number of winding hooks increases correspondingly, thus increasing the deformation force, friction force and fiber displacement resistance.The density of the nonwoven filter material increases, the pores between fibers decrease, the air permeability decreases, and the filtration efficiency increases.4. Fiber network area density and thickness With the increase of area density, the thickness of the material also increases, the permeability of the filter material is reduced, and the filtration performance is improved.Because when the surface density and thickness of the filter material increase, the structure of the material becomes compact, the number of fibers per unit area increases, the fluid channel decreases, and the resistance of the fluid through increases.Also, as the total surface area of the fibers increases, so does the area of trapped particles, making it easier to intercept aerosol particles.When the same air velocity passes through the fiber layer, the thicker the material, the greater the fiber resistance is overcome, resulting in an increase in filtration resistance.5. The surface morphology of the fiber determines the surface area of the fiber.The fiber surface area is large, the collision and capture chance between particles and fiber are large, and the filtration efficiency is also high.The fiber surface is smooth and the fluid resistance loss is small.The surface of the fiber is rough, the porosity is low, and the pressure difference is poor.The fiber surface shape mainly refers to the longitudinal shape and cross section shape of the fiber.The fiber surface shape is more sensitive to pressure drop than to capture efficiency.Longitudinal shape mainly refers to the longitudinal grooves of a fiber, such as viscose fiber.The cross section variation of fiber, also known as profiled, mainly has two forms: one is non-circular cross section shape, which is divided into profiled cross section fluctuation and profiled diameter asymmetry;The second is the hollowness and composability of the fiber.Hollow fiber has the advantages of large fouling capacity, strong adaptability, low cost and long service life.Although the internal structure of hollow fiber filter material has a great influence on the capture of large particles, but the capture of fine particles is more difficult, so it is rarely used in the field of filtration.Because the profile-section fiber has a larger specific surface area than the traditional circular fiber, which improves the porosity, particle carrying capacity and collection efficiency of the filter material, people are more and more interested in the profile-section fiber.Profiled fiber has excellent properties such as stain resistance, bouffant air permeability and good adsorption performance.It has been widely used in filtering field.It is an ideal raw material for nonwovens.Profiled fiber manufacturing technology has less investment and quick effect.It is a very promising differentiated fiber.Common textile profiles include triangle, polygon, three-leaf, multi-leaf, cross, flat, round hollow, meter, C, I, Y, X, H, T, five-ring, U-shaped, dumbbell and so on.By adjusting spinning process parameters (such as spinneret hole shape, polymer mole mass, spinning temperature, melt pressure, spinneret drawing ratio, cooling conditions, etc.), fibers with different cross sectional shapes can be produced.For example, y-shaped spinneret holes can be used to obtain y-shaped and triangular fiber sizes