Study On Properties Of CNT-CNCs/WPU Composite And Construction Of Strain Sensor

Strain sensors can transform mechanical signals into electrical signals,which have great prospects in human motion detection,electronic skin,intelligent electronics and other fields.However,most of the strain sensor materials are too soft and rigid,pollutes the environment,or the strain sensor is not sensitive,which can not meet the requirements of strain sensor.Waterborne polyurethane?WPU?is a kind of green,nontoxic and harmless polymer material after polyurethane?PU?.The unique flexibility,corrosion resistance and oxidation resistance of WPU make it a hot material for the research and development of new devices,especially wearable devices.In order to improve the thermal stability and mechanical properties of WPU,cellulose nanocrystalline CNCs was used as the additive.The effect of CNCs modified by chloroacetic anhydride,succinic anhydride and hexanhydride on WPU was studied.The strain sensor based on the enhanced WPU material is used to monitor human motion.The conclusion is as follows:?1?The CNCs were modified by chloroacetic anhydride,succinic anhydride and hexanoic anhydride.By FT-IR spectra,the carbonyl peak at 1738 cm^-1 and the C4 peak in the narrow C1 spectrum fitted by XPS spectra showed that the grafting of anhydrides was successful.Three kinds of anhydrides modified CNCs took place on the surface of CNCs,and did not change the crystal structure of CNCs.Compared with the unmodified ones,the crystallinity of the modified ones decreased slightly.The thermal stability of the modified CNCs was improved,andthe initial and maximum thermal degradation temperature of the modified CNCs were raised to 204.3? and 242.2?respectively,which were 55.8?and 35.7? higher than those of the unmodified CNCs.The initial thermal degradation temperature and the maximum thermal degradation rate temperature of the modified CNCs were 215.2? and 316.7?,respectively,which were 66.7? and 110.2?higher than those of the unmodified CNCs.?2?WPU was synthesized by acetone method,and CNCs/WPU composite with loading of 0.25wt%,0.50wt%,0.75wt%,1.00wt% was prepared.Compared with the pure WPU membrane,the mechanical and thermodynamic properties of CNCs/WPU composite are improved to some extent,which is positively related to the loading amount of CNCs.The fracture strain of the WPU composite?CNCs-b/WPU1.00?modified by 1.00wt% succinic anhydride is 52.15 MPa,which is 1262% higher than that of the pure WPU composite?3.83 MPa?,and 378%higher than that of the WPU composite prepared by 1.00wt% unmodified CNCs?20.31 MPa?.The young's modulus of WPU is also increased to some extent.Therefore,the mechanical properties of WPU are obviously enhanced by the modified CNCs.?3?CNCs-b/WPU1.00 was selected as the substrate of the conductive material,and CNT was used as the conductive medium to construct the strain sensor.In the range of CNT addition,the addition of CNT destroys the thermodynamic and mechanical properties,and with the increase of CNT load,the extent of damage becomes larger.The results of CV curves show that CNT-CNCs/WPU has a double-layer capacitor and good recyclability.According to the results of LED experiment,the CNT-CNCs/WPU material can be cut into any shape and has conductivity.The conductivity increases with the increase of CNT load,and it is proved that the material can conduct electricity normally in water.According to theformula of sensitivity coefficient and the resistance strain curve,when CNT load is0.50g?CNT0.50-CNCs/WPU?,the sensitivity is the highest.CNT0.50-CNCs/WPU can transmit the signals of fingers and elbow joints in the process of flexion and extension sensitively,accurately and repeatedly.