Simulation And Experimental Study On Preparation Of Long Time Electret Fiber By Centrifugal Melt Electrospinning

Polypropylene(PP)is a usual electret material.After charging,it can capture a large amount of charge in the fiber trap to achieve high-efficiency air filtration.In addition to corona charging and other post-treatment,centrifugal melt electrospinning can also realize the charging of PP when fabricating fibers.However,the filtration efficiency of PP is affected by the environment.After being placed for a while,the charge in PP will attenuate and dissipation significantly,which results in a rapid decline in filtration efficiency.This phenomenon is more likely to occur in an environment with oily particles.The stability of charge in PP is mainly related to the crystallinity of fiber,the depth of the charge trap,and the diffusion of oil mist particles on its surface.Focusing on the above three aspects and combined with centrifugal melt electrospinning,this paper has carried out three parts of research work,and the conclusions are as follows.Firstly,the relationship between the parameters and fiber jet orientation in centrifugal melt electrospinning is studied by dissipative particle dynamics.The results show that the fiber orientation in the two simulation systems increases gradually with the increase of electric field force coefficient,molecular chain length,and temperature coefficient.With an increase in rotating speed,the effective stretching and better orientation performance of fiber jet need to be realized under the combination of electric field force and centrifugal force.With the increase in electric field force coefficient,the electric field distribution in different simulation systems superimposed with the pulsed electric field shows quite other effects on fiber orientation.Then,different PP systems are constructed by molecular dynamics simulation.The calculation of trap depth shows that in a PP system,with the gradual increase in temperature,the trap depth increases gradually,and the maximum value appears at 398 K.The calculation of the diffusion coefficient of oily particles in different PP systems shows that the diffusion is the least likely to occur in the system with PTFE content of 8 wt.% and in the system in which orthophosphoric acid molecule is connected with PP molecular end group carbon atom.And the diffusion of oily particles is more affected by free volume distribution.Finally,PP fibers and PP fibers with three electret additives were successfully prepared by centrifugal melt electrospinning.And their morphology,diameter,chemical structure,and crystallization thermodynamic behavior were characterized and analyzed.The results show that the increase of voltage promotes the change of fiber crystallization from α-crystal to quasi hexagonal crystal.With an increased spinning speed and spinning temperature,the content of α-crystal in fiber increases gradually,and the crystallization is more sufficient.When polytetrafluoroethylene(PTFE)and POLY1001 electret additives were added to PP,the type of the fiber crystal was α-crystal,fibers melting and crystallization requires more energy.When TF-23 electret additive was added to PP,the crystal form of the fiber was quasi hexagonal crystal,in which the melting enthalpy and crystallization enthalpy decreased.The addition of three additives increased the crystallization temperature of the fiber.Finally,the surface potential attenuation of the fiber was tested.The results show that when 1 wt.% PTFE was added to PP,the best electret performance was obtained.For TF-23 additive and poly1001 additive,the content of 1.5 wt.% is the best add value.