| In this paper,fluoropolymer resin/glass fiber composite filter materials and PTFE foam coating filters were prepared by powder sprinkling coating and foam coating processes via using finishing agents including FEP powder,PTFE powder and PTFE suspension dispersion and the non-alkali glass-fiber-woven fabric as substrate,respectively.The process parameters were optimized through orthogonal experiments and the influences of process parameters on the features of the filter materials were analyzed.Moreover,the air permeability,filtration performance,pore size and distribution,morphology,tensile strength,heat resistance,acid and alkali resistance of obtained samples were measured and analyzed,which was compared as well.The main conclusions are as follows.For the FEP/PTFE powder-sprinkling coating composite materials,the mixing ratio of PEP/PTFE resin,molding temperature,and pre-molding time are important parameters affecting filters' air permeability.The air permeability of the filter decreases with the increase of FEP/PTFE mixing ratio.When molding temperature ranges from 270 to 290 o C,the air permeability decreases with the molding temperature increasing.As the [240 s,560 s] pre-pressing time interval studied in this main text,the air permeability of the filter decreases with the increase of pre-pressing time.It is found that the filter material obtained under the molding temperature of 28 oC,pre-pressing time of 320 s exhibits high filtration efficiency and low resistance.For FEP/glass fiber composite materials,which were prepared by plate molding and oven melting process,the coating times,molding temperature,molding time and molding pressure are the main process parameters affecting the permeability of the filter.The multi-factor orthogonal experiment shows that the parameters were listed as following with decreasing significant index:coating times,molding temperature,molding pressure and molding time.Coating times and molding temperature have a significant impact on the permeability of the filter.The study showedthat 5.33 mm/s is an air permeability limiting index for filtering high quality materials.Electron microscopy images illustrate that the plate molding composites holds better,multi-porous structure than samples produced through oven melting process.The high temperature resistant PTFE foam coating filter materials were produced with PTFE foaming solution via mixing PTFE suspension dispersion and functional additives.The study of the materials demonstrated that,(a)Poly-acrylamide showed better performance than Guar-gum on maintaining the stability of foam(b)In the multi-factor orthogonal experiment,the parameters were listed in an effective order as below: the mass fraction of polyacrylate(TT-935),APAM,potassium laurate soap,FSN-100,within air permeability as the evaluation index.When four additives' mass fraction(APAM,TT-935,FSN-100,lauric acid potassium)were 4%,5%,0.1%,1.4%,respectively,we can obtain the samples with best permeability.Within filtration efficiency as the evaluation index,the parameters were listed in an effective order as below: the mass fraction of lauric acid potassium soap,APAM,FSN-100,TT-935.When four additives' mass fraction(APAM,TT-935,FSN-100,lauric acid potassium)were 4%,5%,0.1%,1.4% separately,we will attain the samples with best filtration efficiency.(c)Comparing with the basic fabric,the samples with best permeability showed the increase of 7.43 times' filtration efficiency,in the meantime,with the drop of 2.79 times' air permeability,which shows better air permeability performance than the samples with best filtration efficiency.(d)The material displayed good acid and alkali resistant characteristics,and excellent high temperature resistance in the 250 o C environment.In summary,the basic fabric's filtration characteristics promoted obviously after FEP plate molding and PTFE foam coating finishing.Meanwhile,the material's air permeability was outstanding as well.Thus,the two materials could be potentially used for industrial manufacture. |
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