Research On The Electret Process And Air Purification Efficiency Of Melt-blown Polypropylene Filter Materials

Haze has been serious in recent years,air quality problems affecting people's health at any time.Filter materials for air purification play the key role in household air purifier and personal protective equipment.Polypropylene melt-blown filter material was widely used in many fields due to its high efficiency and low resistance performance.But the existing electrostatic methods still has some technical problems remain to be improved,such as the uneven distribution of charge on the processed materials and the poor charge storage stability.These factors influence the performance and development of this material.To improve the electret process and improve air purification effect of the material,in this paper,polypropylene melt-blown filter material is processed by the ion electret method and the electric field electret method,and their filtration efficiency are measured separately.The electrostatic filtering mechanism has been analyzed combined with the characteristics of the material charge.The results show that the filtering material is difficult to capture fine particulate matter(PM2.5)only by mechanical filtering mechanism.After treating by two methods,the filtration efficiency of the material increases greatly:(1)After processing by the ion electret method,the material increases both space charges and polarization charge.Space charge is also known as surface charge,which is the charged particle settled to the materials in the process of ion electret method.The material's electrostatic filter effect increases greatly,especially for fine particulate matter.But the material's surface charges decay gradually over time and the filtration efficiency also decreases.(2)The space charge of material is strongly influenced by the external environment.When the environment humidity is high,the space charges decay rapidly.Folding structure can effectively reduce the attenuation velocity of material's surface charge.(3)After processing by the electric field electret method,the material only increases the polarization charge,but the polarization charge can last stability.Relative to the ion electret method,the polarization charge's distribution of the material by the electric field electret method have better evenness and orientation.(4)The electrostatic filter effect mainly come from the electric fields inside the material induced by the space charge and the polarization charge.