Study On Gas Sensitive And Humidity Sensitive Properties Of PA66 Composite Bundles

Electrospinning,which is under the action of electric field,producing many small charged jets in the solution or melt.When the jet propagates in the air,the solvent evaporates,leaving a charged fiber that can be deflected or collected on the metal screen or metal device.Fibers with different cross section shapes and sizes are made of different polymers.In addition,the electrospinning process conditions also affects the size of fibers.The diameters of these fibers are between 0.05 and 5 microns.Electrospinning has attracted more attention in recent years due to its versatility and application potential in various fields.It is notable that applications of electrospinning include sensors,filtration,tissue engineering,wound dressing,drug delivery,and so on.Because of its small size,high specific surface area,adjustable porosity and nanofiber composite ability,the electrospun fiber has been widely concerned in the field of sensor,Comparing with traditional technology.Most sensors are designed to be based on the principles of physical adsorption and chemisorption between molecules and sensors.Some characteristics of electrospun fibers are conducive to improving the sensitivity and response speed of sensors.In recent years,nanomaterials prepared by electrospinning are widely used in gas sensors,humidity sensors,etc.,and because of the characteristics of nanofibers,they will make great difference in the field of sensors.Carbon nanotubes(CNTs)is a kind of special structure of one-dimensional nano materials,owning a very large surface area,excellent mechanical properties and conductive properties.With the research of carbon nanotubes,its broad prospect of application has been demonstrated,including the preparation of different kinds of sensors.Composites prepared by combining carbon nanotubes and electrospinning technology is an effective way to prepare sensors.The traditional nanofibers are collected in a form of nonwoven fabrics and the nanofibers are nonuniform random arrays.Nonwoven fabric has relatively low mechanical strength and large area,which greatly limits the application of electrospun nanofibers in many aspects.Incorporating carbon nanotubes directly into polymer spinning solution is easy to agglomerate.It not only makes polymer spinning fibers difficult to collect,but also leads to a common attenuation of mechanical and electrical properties of composite materials.Therefore,it is not an effective method to incorporate the carbon nanotube into the polymer spinning solution directly to prepare the conductive nanofiber composites.In the process of preparation of this paper,we choose the conventional spinning material nylon 66(PA66)as the raw material.Under the process of heating and stirring,we put PA66 particles of certain quality into formic acid to prepare spinning solution in certain concentration.The homemade electrospinning device was used for the preparation of PA66 nanofiber bundle.Then PA66 nanofiber bundle was dipped into the carboxyl carbon nanotube dispersion.After a period of time ultrasonic treatment,two ends the fiber bundle loaded with carbon nanotube were connected to wire.And then by the infiltration of solution of polyvinyl alcohol(PVA)with deionized water dilute,the fiber bundle was removed out.Finally,after heating and drying of the fiber bundle,we got a linear micro sensor.And we used the prepared sensor to detect humidity changes and a variety of organic gases.The nanofiber bundle of the sensor is prepared by PA66,which is used as a flexible substrate with small size,large surface area and high porosity.And then through the way of ultrasonic to load carboxylated carbon nanotubes,conductive network and sensitive characteristics of composite has a formation.Finally,through the infiltration of dilute PVA solution,PVA is coated on the fiber bundle to improving durability and stability of the sensor.We use prepared sensor to detect humidity changes(11%-84% RH)and a variety of organic gases such as dichloromethane,ethyl acetate and acetone.Overcoming the shortcomings of conventional sensors,the prepared sensor has advantages of simple preparation,low cost,fast response and so on.The response time and recovery time to organic gases were 10~21 s and 8~31 s respectively,and the response time and recovery time to different humidity were 9~24 s and 8~19 s respectively.Because it is a resistance-type sensor,the sensor can meet the low power requirements.The sensor has a small size of approximately 0.1 mm in diameter and 2 mm in length.Such a small sensor can be widely applied to the needed occasion by simple encapsulation,having a bright prospect of application.