| With the progress of the society, people’s standard of living has improved significantly. There are many problems of the natural environment that depended on by humans. Air pollutants was mostly soot, S02, NOx, etc. Bag filter is mainly used to solve this problem. The kinds of fibers used for bag filter are m-aramid fiber, polyphenylene sulfide(PPS) fiber, polyimide(P84) fiber, the polysulfonamide(PSA) fiber, etc. Because aramid fiber has excellent mechanical properties, high temperature resistance, thermal stability and so on and aramid fiber has been widely used.M-aramid fiber, m-aramid base M-aramid needle-punched nonwovens were taken as the research object, and the physical properties and acid and alkali resistance of the aramid fiber were tested and compared with the PSA fiber, PPS fiber and P84 fiber. Physical properties, permeability, pore diameter size and distribution, filtration performance of m-aramid base aramid needle-punched nonwovens were tested and compared with PTFE base m-aramid needle-punched nonwovens. For data analysis, research results are obtained.The research contents and conclusions of this article have the following several aspects:(1)the physical properties of the m-aramid fibersSurface morphology, tensile properties and thermal performance of aramid fiber were tested.From the perspective on the surface morphology, m-aramid fiber surface is smooth. Tensile strength of aramid fiber is 8.89 cN, initial modulus of 47.58 cN/dtex, which makes its products are not easy to deformation. The DSC curve of m-aramid fiber showed that the glass transition temperature Tg was 275.3℃, TG curve showed that the initial decomposition temperature of 447.9 ℃, m-aramid fiber has good heat resistance.(2) the acid and alkaline of m-aramid fiberUsing 3 mol/L, 6 mol/L, 9 mol/L H2SO4 solution, 2 mol/L, 4 mol/L, 6 mol/L NaOH solution, dealing with 24 h under the temperature of 20℃, acid and alkali resistance of m-aramid fiber were tested. Compared and analysed the surface morphology, mechanical properties of m-aramid fibers that were treated with different concentrations of H2SO4 solution soaking and NaOH solution.After dealing with the different concentration of H2SO4 solution, surface morphology of m-aramid fiber changed significantly. After the treatment of 9 mol/L H2SO4 solution, the longitudinal grooves were deeper, powerful keeping rate and elongation rate decreased to less than 70%. After dealing with the different concentration of NaOH solution, m-aramid fibers were severely corrosive and produced groove and local sag. After dealing with the 6 mol/L NaOH solution, strength retention rate dropped to below 80%, and the elongation rate remained at 90% above.(3) the physical properties of m-aramid base m-aramid needle-punched nonwovensSurface morphology, tensile properties, thermal performance of m-aramid base aramid needle-punched nonwovens were tested.Surface morphology of M-aramid base aramid needle-punched nonwovens not singeing were smooth and had grooves along the fiber longitudinal. Surface morphology of Singeing had more head end, holes damage, parts of the fibers were lumen and this three-dimensional structure can increase the filtering effect of impurities in the air. The transverse rupture strength is 11.8 MPa, the longitudinal fracture strength is 9.1 MPa, it is more suitable for the external larger stress. From the DSC curve of the m-aramid base m-aramid needle-punched nonwovens, it is obtained glass transition temperature Tg was 273.2 ℃, the TG curve showed that the initial decomposition temperature of 442.7 ℃,so it is more suitable for high temperature conditions.(4) the filtering performance of m-aramid base m-aramid needle-punched nonwovensTaking the residual resistance, permeability, pore diameter and soot cleaning cycle as indicators to character of filtering properties of m-aramid base m-aramid needle-punched nonwovens. Tested and evaluate m-aramid base and PTFE base m-aramid needle-punched nonwovens.The permeability of m-aramid base m-aramid needle-punched nonwovens was 371.37 mm/s, pore size distribution was 9.75 to 72.25μm. The permeability of PTFE base m-aramid needle-punched nonwovens was 302.65 mm/s, pore size distribution was 7.11 to 64.90μm.Thus, the permeability of m-aramid base m-aramid needle-punched nonwoven was bigger, the pore size distribution is wider. So it is obtained that most of the gas flow through the large diameter pores. Under the same test conditions, the initial dynamic dust filtering efficiency of m-aramid base and PTFE base m-aramid needle-punched nonwovens respectively were 99.957% and 99.957%. They all had reached the standard of dust, but the gap was very small. The average pore diameter of m-aramid base m-aramid needle-punched nonwovens was greater than PTFE base m-aramid needle-punched nonwovens 3.76μm, which made dust is easier to filter, so the soot cleaning cycle is shorter. Both in the formal testing phase residual resistance is much greater than the initial test phase, which is due to 10,000 pulse cleaning filter material aging process made the internal structure had changed, it is easier for dust to access to the filter inside. |
PDF Full Text Request