| At present,the flexible piezoresistive sensor materials prepared by domestic and foreign researchers and relevant units through the composite of reduced graphene oxide(RGO)and organic polymer porous materials have some problems,such as poor temperature resistance,narrow applied temperature range and low sensitivity of micro-pressure sensing.In order to solve the above problems,new polyimide(PI)foam with special pore structure and molecular structure was designed and prepared by using microwave foaming technology.Relying on the new PI foam open pore structure,the adhesion amount of RGO sponge in PI foam substrate can be improved.Based on residual ester ammonium salt in PI resin functional groups,induced formation of RGO sponge pleated stacked structure.Finally,through simple,non-toxic and pollution-free hydrothermal reduction and freeze-drying process,the RGO/PI composite sponge with greatly improved compression sensitivity was obtained.Based on the microwave foaming technology of PI foam,by controlling the microwave power and curing temperature,the PI foam with a hole degree of more than 90%can be obtained,and the RGO sponge can be evenly filled in the PI foam hole and the framework,thus effectively improving the sensitivity of the sensor.The residual ester ammonium functional group was obtained by controlling the degree of imidization,which not only improved the hydrophilicity of PI foam,but also induced RGO sponges to form pleated stacked structure through hydrogen bonding.The uniformity of GO dispersion to PI foam impregnation was solved by adjusting the vacuum impregnation temperature,vacuum degree and other conditions,and quantitative impregnation of GO dispersion was realized.The results showed that when the vacuum degree was 80 k Pa and the impregnation temperature was 70?,GO dispersion had the highest transmittance and the best impregnation effect.A series of RGO/PI composite sponge undr different hydrothermal temperature were prepared by hydrothermal method.Through characterization of the structure and performance of different RGO/PI composite sponges,it was determined that the composite sponge flexible sensor prepared at 160?had the best conductivity and the highest pressure sensitivity The temperature resistance test showed that the prepared RGO/PI flexible piezoresistive sensor had good performance in high temperature and low temperature,and maintained its original compression sensitivity after being treated at-196?and 300?.By adjusting the concentration of GO dispersion,RGO/PI composite sponges with different RGO compositions were obtained.With the increase of GO dispersion concentration,the conductivity of composite sponges and the pressure sensitivity within 0-1 k Pa showed a trend of first increasing and then decreasing and then gradually stabilizing.When the concentration of GO dispersion was 3 mg·m L-1,the conductivity of composite sponge was up to 10.68×10-4 S·m-1,and the pressure sensitivity was as high as 1.172 k Pa-1 at 0-1 k Pa,which increased by 100.3-300.6%compared with the previous flexible piezoresistive sensor of polymer/RGO composite sponges.The compression repeatability of RGO/PI-3 and the ability to detect micro-stress were characterized.The results showed that RGO/PI-3 could be applied in both the forward and reverse directions of stress changes,and it had good compression cycle stability and high service lif.It can also show obvious response to impacts such as weak airflow. |
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