Study On Preparation And Properties Of 3D Printed Conductive Rubber

With the rapid development of science and technology,flexible electronic products have entered people’s daily life.Polymer matrix composites have been widely applied as various electronic components,including tactile sensors,capacitors and flexible circuits.As a representative of them,conductive rubber with some unique mechanical,electrical and thermal properties,has been widely used in the fields of sensing,electromagnetic shielding and absorbing materials.The rapid development of advanced production technology enriched the preparation of conductive rubber,whereas there are few studies on the 3D printing technology of liquid conductive rubber.In this project,conductive rubber was prepared by 3D printing process.The printing of liquid conductive rubber was achieved through the exploration of the formula and printing parameters.The basic performance of the 3D printing products was further evaluated.The resistance-response behaviors of the printed products under external fields were studied as well.Finally,printed products were applied to prepare temperature and mechanical sensors.The printability of liquid conductive rubber was determined by its formulation as well as the printing parameters.The high aspect-ratio conductive carbon fibers ensured the liquid conductive rubber with a suitable viscosity and thixotropy.The thixotropic agent further improved the thixotropy and made it with a good printability.The printing parameters determined the quality of the conductive rubber printing products.The carbon fibers in the conductive rubber were oriented in the printing direction which led to the anisotropy of conductive rubber.In the orientation direction,the composites exhibited a better electrical properties and mechanical properties.The fractographs of the conductive rubber when stretched in different orientation were different,where the fibers were pulled out and the fracture was uneven when the printed conductive rubber was stretched along the orientation,Whereas the fracture was flat and the carbon fiber played a role of destructing matrix when it was stretched in the vertical direction.3D printed conductive rubber showed some resistance response behaviors to the external fields.The conductive rubber had an extremely high sensitivity to the tensile stress,where its relative resistance could reach up to thousands of times as the strain raised to 40%.The conductive rubber was featured with negative pressure resistance effect and resistance hysteresis when compressed,and it could maintain a good resistance reversibility after being twisted,bended and cyclic folded.The conductive rubber with a PTC effect which had a good PTC repeatability at 20~100°C.The resistance creep was small at 20~80°C,and the resistance raised greatly at 120°C.After the heating process,the resistance recovered slowly under no touch of conductive rubber.Even after 12 h cooling could not return to its initial electricity,however,its resistance value recovered quickly after being touched.And it basically reverted to the initial resistance value after 14 times cyclic bending.When the conductive rubber was connected with various constant DC voltages,the current value would decrease slightly as the time,which was due to the approaches of the carbon fibers in the conductive rubber.Sandwich strain sensors and temperature sensors were printed,whose resistance value behaved a good response to the external loading and temperature,and its resistance value could change with the wrist movement and temperature respectively.