Preparation Of Conductive Polyurethane Foam And Research On Piezoresistive Sensor

The strain sensor is a device whose resistance changes with the change of the deformation variable under the stimulation of external force.It is widely used in the fields of health monitoring,human motion detection,human-machine interface interaction and flexible bionic robots.However,the flexible materials currently used in strain sensors have the disadvantages of poor mechanical stability and slow pressure response.Therefore,it is of great significance to prepare a strain sensor with high mechanical stability and fast response.Polyurethane foam(PUF)has excellent mechanical stability and good pressure dependence,and can be used as a candidate material for piezoresistive sensors.When subjected to external pressure,the cells shrink,and more foam skeletons "contact" each other;when the pressure is released,the cells recover,and the foam skeletons are separated by the cells to form a "separated" state.This "separation-contact" state formed by changes in external pressure or stimuli enables polyurethane foam to transmit signals in real time when used for strain sensors.We prepared open-cell polyurethane foam loaded with reduced graphene oxide(rGO)into conductive polyurethane foam,and performed a series of performance characterizations on the obtained polyurethane composite foam.The work is as follows:(1)Polyurethane foam(PUF)was prepared by prepolymer method,and hydrophilic polyurethane foam(PUF-SA)was obtained by introducing sodium alginate(SA),and the effect of sodium alginate on foam structure was explored.Through a series of characterizations,it is found that sodium alginate can improve the open cell rate of polyurethane foam.In the water absorption test,it is found that sodium alginate can improve the water absorption performance of polyurethane foam.When the amount of sodium alginate introduced is 2%,the water absorption of polyurethane foam The rate reached 16.793 g/g.(2)Conductive polyurethane foam(PUF-SA-rGO)was prepared by impregnation method.Microscopic observation revealed that the foam was composed of continuous cell walls and open-cell structures,and rGO was uniformly dispersed on the polyurethane backbone.This is due to the open-cell structure and high hydrophilicity of the polyurethane foam,which enhances the adsorption and loading capacity of graphene.In the conductivity test,it was found that the conductivity of the PUF-SA-rGO foam increased with the increase of the amount of deformation.When the amount of compression deformation was 1%,the current value was 13 ?A,and when the amount of compression deformation was 70%,the current value was 13 ?A.value up to 100 m A.Moreover,its electrical conductivity increases nearly linearly with the increase of compression set,and the change range of electrical conductivity is 0.013 S/m-0.115 S/m under 20%-70% compression set.This is due to the increase in the contact area of the rGO supported on the polyurethane foam backbone with the increase in the amount of compressive deformation,and its electrical conductivity increases.In repeated 100 compression cycle tests,the current almost did not decay,indicating that the stability of the syntactic polyurethane foam is good.In addition,when the composite polyurethane foam is applied to the human body motion sensor,the change signal can be quickly detected during the bending motion of the finger and the wrist;the response time and recovery time of the current to the compressive strain are both 100 ms.In addition,the conductive foam has great potential in pressurecontrolled switches.In the test as a pressure-controlled switch,the brightness of the LED light gradually increased with the increase of pressure.