Study Preparation And Properties Of Flexible Strain Sensing Materials Based On Carbon Nanotubes

As the tentacles of the internet of things,sensor is facing a new development opportunity.With the development of the wearable industry,the flexible resistance-strain sensor shows broad application prospects in the fields of human body wearable real-time monitoring,robot bionic skin,medical health tracking,moving limb capture and production vibration detection,etc.Conductive polymer composites are the most commonly used core materials for the flexible resistance-strain sensor,which possess the advantages of good flexibility,large strain detection range and low cost.The conduction mechanism,conductive filler,polymer matrix and preparation process of conductive polymer composites for flexible resistance-strain sensor are summarized and analyzed,we have found that the current flexible conductive polymer composites,as flexible strain sensing materials,have always faced a problem of short service life.Under long-term strain sensing,the composite materials will experience strain sensing instability,and the material structure will collapse or fracture.Therefore,this paper specifically prepares flexible polymer conductive composites by comparing and screening multi-walled carbon nanotubes(MWCNTs)with good performance and mixing them with silicone rubber(HTV),methyl vinyl silicone rubber(MVQ),and natural rubber(NR).The specific researches in this paper as follows:(1)We prepared HTV/MWCNTs conductive composites.Three types of MWCNTs with the same length and different tube diameters were compared to improve the properties of the HTV polymer matrix.The properties of HTV/MWCNTs were studied.By testing the mechanical properties,electrical properties,tensile strain sensing performance,compressive strain sensing performance,tensile strain sensing performance at different ambient temperatures,and loss factors of HTV/MWCNTs composites,the MWCNTs of three different tube diameters were analyzed.Impact of composite materials.It was found that among the three types of MWCNTs,the composites made by TNIM1 and HTV with the smallest diameter are better than the other two MWCNTs.When the amount of TNIM1 is 10 phr,the volume resistivity of the composite is 0.147k?·cm,and the elastic modulus is 9.65MPa.When studying HTV/MWCNTs with different tube diameters,it was found that the smaller the tube diameter,the smaller the loss factor,the larger the amount of MWCNTs added,the larger the loss factor,and the worse the fatigue resistance of the composites.In tensile and compressive strain sensing tests,HTV/MWCNTs were stretched to 100%strain.In 20,000 cycles of tensile sensing,the resistance continues to decrease.After 10,000 times of stretching,the resistance decreases gently,and compressive strain sensing.The same goes for resistance changes.As a flexible strain sensor,long-term stable work that needs to be improved.(2)We prepared MVQ/CCB/MWCNTs composites.By analyzing mechanical properties,electrical properties,and SEM,we found that the two-component conductive filler can greatly improve the conductive properties of the composite materials.Cooperative conductive networks are more stable.Through long-term cyclic compression tests,it was found that MVQ,as an elastic matrix of FCPCs for compressive strain sensors,can stably perform strain sensing under 1.1 million compressions,and the peak resistance of compression sensing remains basically stable under different ambient temperatures.(3)We prepared NR/CCB/MWCNTs composites.Through tensile stress relaxation and electrical performance testing,we found that the two-component conductive filler makes the composite material obtain more stable resistance and tensile stress in tensile stress relaxation.The CCB:MWCNTs filling amount is 30:2 part,the volume resistivity reached 4.6 k?·cm,and the tensile stress was stable atl MPa when the tensile strain was 100%.As FCPCs used as tensile strain sensors,after 20,000 cycles of tensile strain sensing tests,it was found that the composite materials with a 30:4 CCB:MWCNTs addition had better tensile strain sensing stability and linearity.We summarized the above experiments and found that MWCNTs are used as conductive fillers,the smaller the diameter of the MWCNTs,the smaller the percolation threshold;the two-component conductive fillers of CCB and MWCNTs are easier to obtain composites with better conductivity;As FCPCs for compressive strain sensors,MVQ has better fatigue resistance as an elastic substrate and more stable long-term compressive strain sensing performance;As FCPCs for tensile strain sensors,NR as an elastic matrix has more stable sensing performance in long-term tensile strain sensing work.