Preparation And Properties Of TPU Dielectric Elastomer Composites

Dielectric elastomer(DE)materials can realize the conversion of mechanical energy and electrical energy.However,in practical application,the voltage required to be applied is often very high and there are great safety risks.The solution to this problem can be achieved by improving the electromechanical sensitivity of dielectric elastomer materials,which means increasing the dielectric constant or reducing the elastic modulus.In this paper,thermoplastic polyurethane(TPU)with good processing property and relatively high dielectric constant is selected as the matrix,and carbon nanotubes(CNT)and high dielectric ceramic filler titanium dioxide(TiO2)were filled to prepare the dielectric elastomer material with high dielectric constant.The main research contents are as follows:(1)CNT is filled into TPU matrix to prepare TPU/CNT composites.The effects of speed and temperature on the properties of TPU/CNT dielectric elastomers were investigated.With the increase of rotational speed,the permittivity,dielectric loss,conductivity and stress with fixed elongation of composites increase.At the speed of 110rpm,the electromechanical sensitivity of the material is maximum,while the dielectric loss is low.When the rotational temperature increases,the permittivity,dielectric loss and conductivity of TPU/CNT composites decrease,and the stress with fixed elongation decreases.At the temperature of 220?,the composite has high electromechanical sensitivity at low dielectric loss.(2)TiO2 was filled into TPU matrix to prepare TPU/TiO2 composites.The effects of speed and temperature on the properties of TPU/TiO2 dielectric elastomers were investigated.The permittivity,dielectric loss and stress with fixed elongation of the composite increase with the increase of rotational speed.At the speed of 100rpm,the electromechanical sensitivity of the composite is the highest,while the dielectric loss is kept very low.At the temperature of 210?,TPU/TiO2 composites have high electromechanical sensitivity and low dielectric loss.(3)When the content of CNT increases,the permittivity,dielectric loss and conductivity of TPU/CNT composites increase gradually.The composite with CNT content of 1.5wt%has a large dielectric loss,and the conductivity increases obviously.The driving strain of TPU/CNT composites with 1.5wt%CNT added is 2.23%at 5kV/mm electric field,which is nearly twice that of pure TPU(1.2%at 10kV/mm).(4)With the increase of TiO2 content,the permittivity of TPU/TiO2 composite gradually increases,while the dielectric loss and conductivity remain at a very low level.When 50wt%TiO2 was added,the TPU/TiO2 composite has the highest electromechanical sensitivity,and the driving strain is 2.56%under a low electric field(10kV/mm),which is 2.1 times that of pure TPU.(5)The addition of dioctyl phthalate(DOP)into TPU/TiO2 composites can effectively reduce the entanglement of TPU molecular chains.When the DOP content increases,the elastic modulus of material decreases,the permittivity increases.The elastic modulus of which has 25wt%DOP is reduced by 32%compared with that of the TPU/TiO2 composite without DOP.