Preparation And Properties Of Graphene-Waterborne Polyurethane Strain Sensor

In the whole life cycle of civil engineering structure,large deformation and even wide cracks may occur due to the continuous action of load effect and environmental erosion.In view of this situation,the health monitoring of civil engineering structure and the measurement of its real stress and strain state can provide scientific basis for operation and maintenance personnel to make correct decisions,so as to reduce the occurrence of accidents and disasters.However,due to the small measuring range and low sensitivity of the traditional strain sensing device,it is not able to effectively monitor large deformation or wide cracks.Therefore,it is necessary to develop a strain sensing device with large measuring range and excellent performance to meet the health monitoring needs of civil engineering structure.In view of the above requirements,this paper prepared graphene-waterborne polyurethane strain sensing element by combining the excellent conductivity of graphene with the high elasticity and good film-forming property of waterborne polyurethane,and tested and analyzed its performance.The main research contents of this paper are as follows:（1）By analyzing and studying the factors affecting the preparation of graphene-waterborne polyurethane strain sensing element,the dosage of each component in the preparation process and the preparation process parameters were determined.The results show that:Among the four dispersants,polyvinyl pyrrolidone（PVP）,polyoxyethylene nonylphenyl ether（CO890）,cetyl trimethyl ammonium bromide（CTAB）and sodium dodecyl sulfonate（SDBS）,PVP had the best dispersion effect on graphene,and the ratio of PVP to graphene was 1:1.The film forming effect is better when the filling solution blending method is adopted and the ultrasonic time is set to 30min.Through the comparison between the pre-encapsulation method and the post-encapsulation method,it is found that the post-encapsulation method is easy to operate and the conductive film is smooth.（2）By analyzing the resistance change rate curve of the graphene-waterborne polyurethane strain sensor for the first stretch,the test range is determined to be 5%.The initial resistance of graphene-waterborne polyurethane strain sensing element was studied.It was found that the initial resistance increased with the increase of PVP content,and gradually decreased with time,and the initial resistance was basically stable at 12 days.（3）By quadratic polynomial fitting of resistance change rate curve of graphene-waterborne polyurethane strain sensing element,it is found that the nonlinear error of PVP＿1 group is the smallest,which can be controlled within 5%.After five times of pre-stretching,the repeatability error of PVP＿1 group was found to be 20%.（4）Through quadratic polynomial fitting of the resistance change rate curve,it was found that the primary and quadratic coefficients of the fitting curve of PVP＿1 group fluctuated less than those of other groups,and it was finally determined that when the ratio of PVP to graphene was1:1,the strain sensor had excellent stability.At this time,the resistance change rate curve is₀^Δ=-3+219².There are 46 figures,6 tables and 97 references in this paper.