Optimal Design And Performance Research Of Sulfonated Poly (Ether Ether Ketone) Based Humidity Sensor

The real-time monitoring of humidity is very important in all fields of current social development.Humidity sensors have received a lot of attention and applications because they can detect the degree of humidity in different environments.In practical applications,the humidity sensor will be placed in an environment with large changes in temperature and humidity.Therefore,it is quite necessary to develop a humidity sensor with a wide measuring range of humidity,fast absorption and desorption,strong reliability and good long-term stability.Humidity-sensitive materials are an important part of the humidity sensor,and its response to water vapor can directly determine the performance of the humidity sensor.In recent years,many researchers have focused their research on humidity sensors on the development and modification of humidity-sensitive materials.Polymer electrolyte materials have attracted more and more attention in the design of humidity sensors because of their advantages such as wide humidity measurement range,strong structure design,low cost and wide sources.After investigating its humidity-sensing mechanism,it is found that when polymer electrolyte materials are used as humidity-sensitive materials,they have the disadvantages of low linearity in a low relative humidity(RH)environment and poor stability in a high relative humidity environment.Therefore,the preparation of a polyelectrolyte material that not only has the ability to adsorb water molecules but also allows the humidity sensor to maintain good humidity sensitivity under high relative humidity,is very necessary for the development of the humidity sensor.In the structure of the sulfonated Poly(ether ether ketone)(SPEEK)polyelectrolyte humidity-sensitive material,the sulfonic acid group has excellent hydrophilicity,and its hydrophobic backbone also has excellent mechanical properties and chemical stability.Therefore,SPEEK humidity-sensitive materials have the potential for the development and application of high-performance humidity-sensitive materials.In view of the structural advantages of SPEEK polyelectrolyte materials,this paper mainly focuses on the application of SPEEK polyelectrolyte materials in humidity sensors.It starts from the characterization of materials,the testing of humidity sensitivity and the research of humidity sensing mechanism.The SPEEK polymer material is obtained through a simple post-sulfonation reaction,and a humidity sensor with excellent humidity sensitivity properties such as a wide range of humidity,short response recovery time,and good long-term stability is prepared through some modification methods.The main contents are as follows:1.First,a simple post-sulfonation reaction introduces sulfonic acid groups into main-chain of polyether ether ketone(PEEK)to obtain the SPEEK humidity-sensitive material.Then through the diazonium salt reaction,p-phenylenediamine(PD)was modified on the surface of graphene oxide(GO),which was prepared by the Hummer method to obtain,functionalized graphene oxide(MGO)with amino functional groups on the surface.Compounding different added amounts of MGO with SPEEK,and using the acid-base interaction between the-NH₂ group in MGO and the-SO₃H group in SPEEK to improve the humidity sensitivity of the SPEEK material.In the paper,composite humidity-sensitive materials with 0%,5%,10%,and 15%of MGO were prepared,and various humidity-sensitive properties of MGO/SPEEK humidity-sensitive materials with different composite ratios were successively investigated.The experimental results show that the performance of the composite membrane humidity sensor prepared by adding MGO to SPEEK is higher than that of the pure SPEEK membrane humidity sensor.Compared with the pure SPEEK membrane humidity sensor,the composite membrane humidity sensor the response/recovery time is shortened from 10 s/500 to 5 s/170 s,and the hysteresis is reduced from 16.0%RH to8.0%RH.2.Through the first part of the experiment,it is found that the combination of MGO and SPEEK can improve the performance of the SPEEK humidity sensor,but the relative longer response/recovery time of the MGO/SPEEK composite membrane humidity sensor limits its application in the field of real-time rapid monitoring.In order to enable SPEEK humidity sensitive materials to be used in real-time,fast and reliable humidity detection fields(for example:respiratory monitoring,non-contact diagnosis and non-contact control,etc.),the next step is to continue to improve the humidity sensitivity of SPEEK humidity sensitive materials.In this chapter for the first time,the SPEEK solution is spun directly on the surface of the clean Ag-Pd interdigital electrode using the electrostatic spinning method to prepare a SPEEK nanofiber humidity sensor with a loose porous structure.Because the loose and porous nanofibers are more conducive to the diffusion and transfer of water molecules,the performance of SPEEK nanofiber humidity sensor is significantly improved compared to the SPEEK dense film humidity sensor in the previous study.However,scanning electron microscopy(SEM)observed a certain amount of beads in the SPEEK nanofiber network,which may hinder the transmission of water molecules.Subsequently,different content of polyvinyl butyral(PVB)was mixed into SPEEK electrospinning solution,the purpose is to reduce the content of beads in SPEEK nanofibers,and further improve the humidity-sensitive performance.By studying the influence of the amount of PVB on the humidity sensing performance of the composite humidity sensor,it is found that the composite nanofiber humidity sensor with SPEEK/PVB=1:3 exhibits a small hysteresis(2.7%RH),excellent stability as well as fast response(<1 s)and recovery(5 s).In addition,this chapter also studies the possibility of its application in respiratory monitoring and non-contact sensing for the SPEEK/PVB=1:3 composite nanofiber humidity sensor.