Preparation And Properties Of Carbon Nanotubes/polyurethane Composite Films And Fibers With Conductive And Electric Heating Functions

In recent years,the conductivity of polyurethane（PU）materials has attracted wide attention.Because of its excellent mechanical properties,elasticity and resilience,conductive polyurethane has wide application prospects in intelligent sensors,body temperature protective clothing,flexible electrodes,anti-radiation and anti-static clothing and other fields.In this paper,polyurethane was used as matrix material and MWCNTs as conductive component to prepare composite films and fibers with good conductivity and electric heating properties.The main research contents and results are as follows:（1）MWCNTs/PU composite films were prepared by dispersing MWCNTs in PU solution.The composite films were characterized by SEM,FT-IR,TG,DMA,mechanical properties and rheological properties.The results show that the elongation and fracture strength increase by 6.8%and 30.7%respectively when the addition of MWCNTs is 1%.The results of infrared spectroscopy showed that MWCNTs increased the hydrogen bonding index of PU from 0.34 to0.43.In the rheological test results,the non-Newtonian index r ises from 0.64 to 0.79 and the structural viscosity index decreases from 8.2 to 4.5 when the temperature is between 20℃and65℃,which can improve the spinnability by increasing the temperature.（2）Conductivity and force sensing properties were studied by conductivity test,tensile test,stress relaxation test and cyclic tensile test.The results show that the higher the content of MWCNTs,the better the conductivity of the composite film,and the percolation threshold is2.8%.The sample has a certain thermal sensitivity,when the temperature rises from 50 to 110℃,the conductivity of samples containing 3%and 5%of MWCNTs increases by 2S·m^-1 and26S·m^-1,respectively.The electric heating phenomenon is obvious.At 30V voltage,the temperature of the composite film with 1%,3%and 5%MWCNTs increases by 0.2℃,10℃and 125℃respectively.In the tensile test,the larger the elongation is,the greater the conductivity decreases,and the maximum decrease is 2.5S·m^-1.In stress relaxation experiments,the electric resistance variations depend on the molecular motion.There are two stages of electric resistance change,which is similar to the stress relaxation process.（3）Conductive polyurethane fibers were prepared by simulated dry spinning and their conductive properties were studied.The results show that the conductivity of the fibers is 2.5 x10^-2S·m^-1,which is lower than that of the composite membranes.When the voltage is 30V,the temperature of the sample fiber rises by 1.5℃.When the temperature of the sample fiber rises from 25℃to 150℃,the electrical conductivity rises from 2.5×10^-2S·m^-1 to 3.0S·m^-1.