Tensile condition of PPS filter material
SFFILTECH polyphenylene sulfide (PPS) fiber filter material is widely used for bag type dust removal of industrial furnace flue gas. It needs to bear various loads during service under complex working conditions, and tensile load is the most common. PPS fiber is combed by the carding machine, the single fiber axis is consistent with the fiber mesh axis, and the fibers are connected end to end to form a single-layer fiber mesh.
The fiber mesh is laid back and forth with the wire laying trolley (the speed of the wire laying trolley is), and moves forward with the conveyor curtain (the speed is). In this way, the fiber axis (the fiber mesh axis) and the filter material axis (the fiber mesh movement direction) form a certain angle (the fiber orientation angle).
After calculation, the orientation angle of SFFILTECH PPS fiber is 5 °. It can be seen that the fiber orientation in the filter material is almost the same as that of the filter material in the transverse direction. After acupuncture, the transverse strength must be much greater than the longitudinal strength. Therefore, plain woven fabric needs to be added between the two layers of fiber mesh to provide the longitudinal strength. In fact, PPS fibers are not completely in a straight and parallel single fiber state after carding by the carding machine. After the two layers of fiber mesh and the base cloth are needled and tangled, with the drafting of the filter material, the spatial state of the single fiber in the filter material structure is more complex, which is difficult to structure modeling.
From a macro perspective, the spatial path and tangle of fibers are ignored, and the filter material is regarded as a whole. Different from the ordinary two-dimensional fabric, the filter material has a three-level structure of “fiber layer – substrate layer – fiber layer” in the thickness direction, and the thickness can not be ignored, so it can be considered as a three-dimensional fabric. Since the structures of filter materials in x, y and z directions are different, the filter materials are orthotropic materials.
1. Seamless line pattern
The longitudinal peak load of PPS filter material is about 1100N, and the peak stress is about 10MPa; The zonal peak load of filter material is about 1300N, and the peak stress is about 13MPa. For longitudinal stretching, the stretching behavior of filter material can be divided into three stages. In the first stage, the load is mainly borne by the substrate, and the fiber has little effect; In the second stage, the composite structure composed of fiber aggregate and substrate bears the load together; In the third stage, the filter material is tightened in the meridional direction, and the load is again borne by the base cloth. For zonal stretching, the stretching curve of filter material can also be divided into three stages. In the first stage, the fiber and the substrate share the load; In the second stage, the load is mainly borne by tightly held needle oriented fibers; In the third stage, the base cloth is not enough to bear the load and starts to fracture. The curve shows zigzag “jitter” until the filter material fails as a whole.
2. Stitched strip
The tensile strength of the suture is essentially dependent on the strength of the suture or the shearing action between the suture and the filter material. The meridional tension is divided into three stages. The elastic stage is the first stage with a large modulus. After reaching the yield point, it enters the plastic deformation stage. The modulus decreases and the load further increases until the suture breaks one by one. When weft stretching, the number of stitches is small, and the stretching process can be divided into two stages. In the elastic stage, the modulus remains unchanged, and the load increases all the time. After reaching a certain extent, the stitches gradually embed into the filter material, and then break one by one until the filter material fails.
3. Shear condition
The essence of shear spline stretching is shear stretching, not axial stretching. The longitudinal initial shear tensile modulus of seamless wire and sewn filter material is consistent; When the strain reaches about 2.6%, there are suture strips that depend on the interlocking effect of suture, with large modulus and strong bearing capacity, and the peak load is about 680N; The seamless line sample has no limit of suture. The filter material has a low modulus until it is sheared and torn. The peak load is about 350N, and then the base fabric is broken one by one. Therefore, in the service process of the filter material, it is necessary to ensure that the stress on the filter material is uniform, so as to avoid the shear effect and failure of the filter material.