Study On Properties And Preparation Techniques Of Polytetrafluoroethylene Triboelectrification Blended Filters By Filling Modification With Nano SiO₂ Powders

Triboelectric effect has been applied widely in air-purified field to improve the filtration performance of filters.It has been proved that the filtration efficiency of materials with triboelectric charges was much higher than that of fabrics with corona static charges.Although the capability of filters to capture fine particles with submicron scale diameter could be modified by triboelectric charge significantly.Nowadays,most air-purified materials are generally manufactured by the melt blown or needle-punching process with single type of polymeric fibers.Even though the filtration quality of these filtration materials could be modified by static charges from the external high voltage source,the service life of the filters is limited due to the dissipation of charges.The low frictional coefficient,high volume resistance and water repellency of PTFE could help the charge exist on the surface for a long time,which effectively elongates the duration of air-purified materials.Therefore,PTFE fiber is an ideal material to manufacture the blended fibers filters with excellent filtration performance.Aiming at modifing the contradiction between the filtration performance and the air flow resistance,in this article,nano SiO₂ powders was employed for filling modification of PTFE resins to prepare modified PTFE fibers with rougher surface,leading to improved triboelectric effect.Research contents are as follows:?1?Explore the preparation techniques of PTFE composite materials such as modified PTFE fibers,and needle-punching filters made of PTFE fibers and synthetic or natural fibers;?2?Compare and analyse the influence of filling modification to triboelectrification performance on PTFE films,the friction and wear mechanism of PTFE materials was analyzed and studied by SEM;?3?Based on the filtration performance of PTFE blended needle-punching filters,analyzing the filtration characteristics of PTFE blended needle-punching filters and the triboelectric effect during filtration process.Influence of filling modification and different contents of powders filled in PTFE on the filtration performance of blended needle-punching filters were also studied.Experimental results showed that:?1?Among five kinds of deputy abrasives?PA,Cotton,PPS,PET,PP needle-punching materials?,the maximum surface charge density of pure PTFE films could be achieved when PA needle-punching materials was employed as the deputy abrasive.At a rate of 5.2m/min,number of cycles of 70,load of 7.7N and contact area of 28.5cm2,the surface charge density of pure PTFE films after friction with the five abrasives would approach to the maximum value;?2?With the increasing of the content of SiO₂,there was a trend that the triboelectrification performance of modified PTFE films improved with the increasing content of SiO₂.Especially with the content of 3.0wt%,the triboelectrification performance of the modified PTFE films could be improved significantly.Compared with the pure PTFE films,the modified ones could produce more charges under milder frictional conditions;?3?With the increasing of the content of pure PTFE,the filtration performance of PTFE blended filters tended to improve and reached the maximum when the content of PTFE was 40wt% or 50wt%,the filtration performance began to decline when the content of PTFE continued to increase.The optimal comprehensive performance could be achieved by blending 50wt%PTFE and 50wt%PA fibers;?4?With the increasing of the content of powders,the filtration performance of modified PTFE blended filters tended to improve,especially when the PTFE fibers with the content of 3.0wt%,the filtration performance of the corresponding filters improved more obviously than pure PTFE blended filters.