Preparation And Characterization Of Multi-layer Superhydrophobic PI Nanofiber Composite Membranes

Polyimide(PI)was widely used in thin films,engineering plastics,fiber,high temperature filtration,protective clothing,coatings,adhesives,Automotive,aerospace and microelectronics devices due to its excellent thermal stability,good mechanical properties,chemical resistance and so on.At present,more and more researchers pay attaention to some special properties of PI,and made it.Some researchers have modified the PI to achieve excellent performances.Composite modification is the most simple and efficient modification methods.In this study,one of commercial PI nanofiber membrane was used as a base material and modified by multi-layer composite to obtain a super-hydrophobic PI nanofiber composite membrane.The PI nanofiber membrane was modified by polyaniline(PANI)to construct the film roughness.After that polytetrafluoroethylene(PTFE)and polydimethylsiloxane(PDMS)were used to reduce the surface energy of the film to obtain a multi-layer super-hydrophobic PI/PANI/PTFE/PDMS composite film.This paper includes the following three Parts:(1)Preparation and Characterization of PI/PANI Nanofiber Composite Membrane:PI/PANI composite membrane was prepared by In situ polymerization of aniline to formrough polyaniline on the surface of PI/PANI fiber membrane.The composite membrane with the sheath-core composite structure combined the excellent properties of the two polymers of PI and PANI.The performance of PI/PANI composite membrane was optimized by the reaction temperature and the concentration of aniline.The results show that the structure and performance of the composite membrane was better when the reaction temperature is 0°C and the PANI concentration is 0.03 M.The surface of the membrane has a nanometer coarse and uniform papillary structure,which meets the requirements of superhydrophobic roughness and the rough structure constructed by PANI can also be processed later.(2)Preparation and Characterization of PI/PANI/PTFE Nanofiber Composite Membrane:PTFE nanoparticles were attached to the surface of the PI/PANI composite membrane by ultrasonic soaking method to reduce the surface energy which named PI//PANI/PTFE composite film.In the first step,the PI/PANI composite membrane was immersed in different concentrations of PTFE emulsion to obtain a PI composite membrane.The results show that the contact angle of the composite film increases first and decreases with the increase of PTFE content later.When the PTFE content reaches 5wt%and heat treatment at 300?,the contact angle of PI/PANI/PTFE composite film was the best,and as high as 157.4~o.(3)PreparationandCharacterizationofPI/PANI/PTFE/PDMSNanofiber Composite Membrane:In order to further improve the performance of the composite membrane and enhance the synergistic effect of the modification of each layer,was used PDMS modification treatment to prepare Superhydrophobic PI composite membrane.The specific method is to ultrasonically soak the optimized PI/PANI/PTFE composite membrane in different concentrations of PDMS emulsion,and then optimize the content of PDMS to obtain PI/PANI/PTFE/PDMS composite membrane.The results show that the contact angle of prepared PI composite film increases first and then decreases with the increase of PDMS content.When the PDMS content is2wt%and the treatment temperature is 300°C,the contact angle is maximum 159.4~o.In addition,PI/PANI/PTFE/PDMS nanofiber composite film also has good mechanical properties.The tensile strength,elongation at break and tensile modulus are 16.2 MPa,61.8%and 108.2 MPa respectively.