| With the development of modern technology science and industrialization level, people's awareness of environmental protection is gradually strengthened. As a result, the world demand of filter materials is rising year by year. Nonwoven materials have replaced the traditional textile filter materials which is used more and more widely as air filtration. Spunlaced nonwovens have been researched by domestic and foreign scholars, however, the structure and performance of nonwovens, especially in filtration field of high temperature industrial were lack of study. Therefore, research on these areas has certain academic and application value.The aramid spunlaced nonwovens as the main research object were tested and analyzed by the equipments of scanning electron microscopy, infrared spectrometer, Topas analysis tester, strength tester and so on. Apparent structure, size stability, pore structure, mechanical properties and other properties were studied in the conditions of high temperature and corrosion. The relationship was analyzed between structure parameters and properties. The results showed that:(1)The aramid spunlaced nonwovens had slightly loose surface after high temperature processing, but changes of fiber structure still can not be found. With the temperature increasing, the thickness and the gram per square meter first decreased and then increased. Vertical and horizontal shrinkage of the sample were less than 5%. Before and after processing, pore size distribution of the samples were in the range of 60-90μm, the average aperture first increases, then decreases. With processing temperature increasing, the permeability first increased, then decreased. Longitudinal and transversel breaking strength increased overall. The longitudinal breaking strength first decreased and then increased while the transverse breaking strength increased constantly. Decomposition temperatures of samples were around 350℃. The beginning decomposition order was as follows: sample in 260℃→sample in 230℃→sample in 200℃→sample in normal temperature.(2)Apparent structural changes unobviously when the concentrations of acid and alkali solution were low, as the concentration of solution increasing, fibers began to appear fissure and the distribution was heterogeneous. Before and after processing the thickness of the sample was fluctuated around 1mm. The CV values of the thickness and the gram per square meter were changed accords with the quadratic curve. With alkali solution process, the dimensional changes after laundering were slightly greater than that with acid solution process, but were not more than 1.6%. Under the same concentration, the permeability with alkali solution process is larger than that with acid solution process. The rate of change in permeability was first decreased, then increased and the minimum was at alkali solution of 10% and acid solution of 30%. The breaking strength and elongation of samples were downtrend. The main vibration frequencys in infrared spectrogram were as follows: 1650cm-1, 1606cm-1, 1533cm-1, 1485cm-1, 685cm-1 and there was no big fluctuations on the peak value.(3)After high temperature and alkali solution process, M value of the samples first decreasesd and then increased while it first increased and then decreased after acid solution process. In 30% of alkali solution and 30% of the acid solution, samples were obviously in longitudinal arrangement and anisotropic property. After high temperature process, the greater the thickness is, the smaller the permeability is. After alkali solution process, the greater the grams per square meter is, the larger the permeability is. With the thickness increases, the permeability first decreases and then increases. Porosity variation presents inverted " N " pattern type while the center distance of fibers presents " N " pattern. The greater the porosity is, the smaller the fluid dynamic coefficient is. After high temperature, alkali and acid solution process, fluid dynamic coefficient presents " N " pattern. |
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