Development Of Flue Gas Filtration Material Based On PTFE Emulsion Foaming Coating

In recent years,with the rapid development of industry,the number of domestic factories is increasing.At the same time,the emission of pollutants such as industrial smoke and dust is also more serious,which not only makes the atmosphere environment seriously polluted,but also poses a serious threat to huma n health.It is understood that thousands of people in the world every year cause various diseases due to air pollution and eventually die,which shows that atmosphere pollution is no longer an insignificant problem,and it is closely related to everyone.Moreover,the solution to the problem of air pollution should be urgently needed.Therefore,developing a highprecision filter material to reduce atmospheric pollution caused by industrial flue gas has become an urgent issue to be solved.In this paper,a variety of different formulations of PTFE foaming coating emulsion were prepared by adding a certain proportion of foaming agent,thickener,foam stabilizer and other functional additives to the pure PTFE emulsion,and then the viscosity tests were carried out separately.The effects of temperature,stirring speed and stirring time on the viscosity of foaming emulsion system were studied,and the viscosity of the PTFE foaming coating emulsion suitable for coating experiment was determined.At the same time,a large number of PTFE foaming coating filter material samples were prepared by foaming coating process.Taking pore size,air permeability and surface morphology structure as the main evaluation indexes,analyzing the influence of the ratio concentration of various functional additives,drying temperature and drying time on foaming coating filter material,and determining the optimum PTFE foaming coating emulsion formulation and foaming coating process.Finally,a complete foaming coating experiment was carried out in combination with the best foaming coating emulsion formulation and the best coating process.A PTFE foaming coating composite filter material was prepared and compared with the blank glass fiber sample and foreign sample.The effect of PTFE emulsion foaming coating treatment and the performance of the foaming coating composite filter material under the optimal formulation conditions were comprehensively evaluated.The main achievements of this paper are as follows:(1)Viscosity study of PTFE foaming coating emulsion: under other conditions,the viscosity of the foaming emulsion system decreases with increasing temperature or stirring speed,and as the stirring time increases,it shows a trend of decreasing first and then increasing.It was found that the mixing time of 2 h and the temperature of 30 °C were suitable when formulating the foaming coating emulsion.At this time,the viscosity of the PTFE foaming coating emulsion was about 900 m Pa·s,which is suitable for coating experiments.(2)The optimum formulation of PTFE foaming coating emulsion was determined: the ratio of PTFE emulsion was 94.5 %,the foaming agent potassium laurate soap was 2.5 %,the foam stabilizer polyol type nonionic surfactant was 2 %,and the thickening agent methylcellulose was1 %.The PTFE foaming coating emulsion prepared according to this formula has the advantages of high foaming speed,big foam content,small diameter and good stability.(3)Study on foaming coating process:(1)The influence of drying process on the air permeability and pore size of coating filter material: within a certain temperature and time range,with the increase of drying temperature,the air permeability of coating filter material decreases gradually,and the average pore diameter increases first and then decreases;with the extension of the drying time,the gas permeability of the coating material decreases gradually,and the average pore diameter decreases first and then increases.(2)The optimum foaming coating process parameters were determined: drying temperature is 310 ℃ and drying time is 60 seconds.The film formed on the surface of the PTFE foaming coating filter material prepared under these conditions has good flatness and continuity,and has a large number of uniformly distributed micro-porous,with a gas permeability of 49.6 mm/s and a pore size of 3.8 μm.(4)2.5 % of a foaming agent,2 % of a foam stabilizer and 1 % of a thickener were sequentially added to a PTFE emulsion having a concentration of 94.5 %,and stirred 2 h at a speed of 500 rpm in a water bath temperature of 30 ℃,the PTFE foaming coating emulsion was obtained,then the surface of the glass fiber was coated and prebaked 2 min at 160 ℃,followed by drying 60 s at 310 ℃to obtain PTFE foaming coating composite filter material.After testing,its air permeability is 60.9mm/s,the average pore diameter is 0.21 μm,which is very close to foreign sample,and the performance is much better than the glass fiber blank sample,indicating that PTFE foaming coating treatment is better and can greatly improve the performance of the glass fiber blank sample.