Preparation And Dielectric Properties Of Thermally Conductive Dielectric Elastomer Composites

The dielectric elastomer is an electroactive polymer material capable of producing a large driving force and driving deformation under the acti-on of an electric field.Because of its excellent functionality,the dielectric elastomer is quite potential in the application of the electronic communications,information enginerring and biomedical field.Especially it's widely recongnized that the dielectric elastomer can be apllied in the drive,sensor and artificial muscle research.It's a common method to produce dielectric elastomers by adding dielectric ceramics to the polymer.The work will produce heat,Whether the dielectric elastomer material is used for the drive,but the single dielectric ceramic/polymer dielectric elastomer composite material has a low thermal conductivity,poor heat dissipation,and poor thermal stability performance,which affect the material life and working hours,and limit the working environment.thus is necessary to add thermal conductive filler to the dielectric ceramic/polymer dielectric elastomer composite to improve its thermal conductivity and thermal stability.The present study,aiming at obtain the best performance of the thermal conductivity of the dielectric elastomer composite material,designed the experiment in the following 3 aspects:?1?SiC/PDMS composites were prepared by blending and hot forming.The silicon carbide?SiC?was a thermally conductive filler and the silicone rubber?PDMS?was a polymer matrix.The structure,dielectric properties and thermal properties of the composites were tested,The experimental results show that the SiC particles can be dispersed uniformly in the silicone rubber matrix by scanning electron microscopy.The test on the dielectric properties found that the dielectric constant of the composites gradually increased with the increase of SiC content.When the silicon carbide loading was added to 50 vol%,the dielectric constant of the composites reached 15.3?100 Hz?.The dielectric loss of the composites increases gradually with the increase of the silicon carbide content,and reaches the maximum value of 0.056?100 Hz?when the volume fraction of the silicon carbide filler is 50%.It can be concluded that the Si C/PDMS composites have a certain dielectric constant and a lower dielectric loss?less than 0.1?.The addition of SiC filler can improve the dielectric strength of the polymer.When the volume fraction of SiC is 30%,the dielectric strength reaches the maximum,and the dielectric strength is 48.41(MV?m^-1).Thermal testing on the material found that,the thermal conductivity of the composites is increased for the SiC filler added.With the content of silicon carbide filler increases,the thermal conductivity of the composites increases gradually.The rising curve is presented in“S”because less thermal conduction path is formed with less silicon carbide content and the thermal conduction path is saturated with relative more silicon carbide content.In the SiC/PDMS composite,when the volume fraction of silicon carbide filler is50%,the thermal conductivity is 1.21?W/m?k?which is 6 times that of pure silicone rubber.The glass transition temperature of the composites also increases with the addition of silicon carbide.?2?The volume fraction of inorganic filler is 50%and the ratio of BT to SiC is different.The structure,dielectric properties and thermal properties of the composites are tested by BT/SiC/PDMS three-phase composites.The experimental results show that the BT particles and Si C particles are uniformly dispersed in the silicone rubber matrix by scanning electron microscopy,and the structure of the two kinds of particles is similar to the gradation effect,which makes the composite structure more compact and which contribute to improving the thermal properties of materials.After the analysis of the dielectric properties and thermal properties of the material,The best overall performance is composites with a filler composition of BT/SiC=35/15.When the content of the filler is BT/SiC=35/15,the dielectric constant of the composite material is 24.5 and dielectric loss is 0.033 at the frequency of 100Hz,dielectric strength of 23.35(MV?m^-1)is 2.2 times the50vol%BT composite material.When the temperature is below 70?,the dielectric constant of the composites with BT/SiC=35/15 is lower than 50vol%composites,but when the temperature is below 70?,the dielectric constant of the composites with BT/SiC=35/15 is higher than that 50vol%composites.As the temperature increases,the dielectric loss of the composite material is very stable at a low level.?3?The BT/SiC/PDMS dielectric elastomer composites were prepared by blending and thermoforming.The inorganic filler was BT and Si C mixed with BT/SiC=7/3.When the content of BT/Si C=7/3 mixed filler is 15%,the composite properties of the dielectric elastomer composites are the best.At this time the dielectric constant and dielectric loss were 7.1 and 0.026?100Hz?.The dielectric constant is nearly 4 times higher than that of pure silicone rubber?1.8?and the dielectric loss remains at a low level,the dielectric strength of 32.67(MV?m^-1)increased by 26%compared with pure PDMS.At this time,the thermal conductivity of the composites is 0.342?W/m?k?,about 1.5 times of pure PDMS,and has excellent thermal stability,With T_5%is 419.4?.The elastic modulus is 1.31?MPa?,sensitivity factor of 5.5 is pure PDMS?2.7?about 2 times.