Research On Several Key Problems About Melt-blown Polypropylene Electret Air Purification Materials In The Process Of Application

In recent years,air pollution has become more and more serious.In order to breath fresh air,more and more devices of cleaning the air,such as individual protective mask and air purifiers,have been used in our daily life.Therefore,people are paying more attention to the air filtration materials.The traditional filter materials mainly rely on inertial deposition,gravity sedimentation,Brownian diffusion and other mechanical action to achieve the purpose of purifying air.To filter small particles such as PM2.5,it is necessary to increase the density of the filter materials,which will increase the filtration resistance and reduce the permeability.However,melt blown polypropylene electret air purification material keep in reserve charge,so there is strong electrostatic field inside the materials.The materials can rely on the electrostatic field to adsorb the small particles.What's more,the electrostatic field also has the function of sterilization.So,melt blown polypropylene electret air purification materials have become a leading product Air purification field because of its excellent performance such as low resistance,high efficiency and antibacterial properties.In the process of application,people found that the filtration performance of the melt blown polypropylene electret air purifying material is greatly influenced by the environment.One is temperature of environment.When the energy of the charges which are in the materials is greater than the trap potential,the charges will escape from the potential well.The filter performance is affected.The other is humidity of environment.The water molecules are adsorbed on the surface of the materials which leads to the increasing of the conductivity of the materials,the charge decrease to affect the filter performance.The filtration performance of different melted electret air purifying materials is different from the environmental impact degree.On the other hand,in order to accurately calibrate the filtration performance of the materials,the standardization and organization in the general filter standard has clearly put forward that the isopropanol charge discharge test(IPA test)is a normative content and the two methods of cleaning up the charge,which are isopropanol solution fumigation and soaking.But the results of the two methods are different.In this passage researched on two aspects by means of the test of the filtration efficiency and resistance,thermally stimulating discharging spectrum,the X ray diffraction spectrum and the scanning electron microscope atlas analysis.One isresearching on the difference about temperature resistance and moisture resistance between different melted electret air purifying materials,and analyzing the reasons for the differences.The other is researching on changes in properties and structure of polypropylene electret air purification materials before and after treatment of isopropanol solution.The main results obtained are as follows:(1)The temperature resistance of different melt blown polypropylene electret air purifying materials is different.It is mainly related to the crystalline structure of the material and the order of grain arrangement.?-crystalline material,good charge storage stability,the temperature resistance of melt-blown polypropylene electret air purification material is good.The order of grain arrangement is better,the temperature resistance is better.(2)The crystal of the melt blown polypropylene electret air purifying material finally turn into the most stable ? crystal after the high temperature treatment.When the crystal transformation is completed,a certain range of temperature treatment will change the order of the grain arrangement and increase the order of the grain.(3)The three areas model of semi-crystalline polymer,namely crystalline region(CR),amorphous region(MAR)and rigid amorphous region(RAR)respectively.The? crystal is relatively stable because of the obvious boundary of crystal region andamorphous region lead to the obvious difference of electrical conductivity.It can form a stable dipole.Other crystalline forms are relatively unstable because the unobvious boundary between crystal region and amorphous region lead to difference of conductivity is small.It cannot form a stable dipole.(4)The temperature resistance of different melt blown polypropylene electret air purifying materials is different.It is mainly related to the phase structure of the material and the thickness of the material.?-crystalline material,good charge storage stability,the humidity resistance of melt-blown polypropylene electret air purification material is good.The thickness of the material is smaller,the humidity resistance is poor.(5)For the melt blown polypropylene electret material,the humidity of the environment is higher,the change of the filtration performance is more obvious.The change of filter performance is related to the amount of charge storage and has nothing to do with the surface potential.This shows that the surface potential can not reflect the charged properties of the material.(6)Isopropanol soaking and fumigating can not change the filtration resistance and crystal structure,and both can achieve the purpose of cleaning up the charge andthe effect of cleaning up the charge is the same.However,isopropanol soaking will cause the swelling of the fiber and roughen the surface of the fiber,and change the non-electrostatic filtration efficiency of the material.