Preparation Of High Dielectric Constant Composite Elastomers And Their Applications In The Field Of Flexible Sensors

With the rapid development of robot industry and the role of nursing robot,drive and tactile sensors in the robot device has received a lot of attention from researchers,and is expected to further broaden the awareness and ability of the robot motion.The core components of the dielectric elastomer with high performance get more extensive research and attention due to simple structure,wide application range,low power.It not only has the advantages of large deformation,fast response speed,high electromechanical conversion efficiency,good load matching,strong environmental suitability,high fatigue life and excellent bionic performance.At the same time,the dielectric elastomers can be used as a mechanical sensor in many emerging research areas including robot tactile skin.It has become the focus of attention of scholars.This paper will use the calcium copper titanate,polyaniline coated calcium copper titanate particles with high dielectric constant,high polar polypropylene glycol diacetate flexible polymers,truxene and poly acetylene conjugated material,carbon nanotubes and polyaniline conductive materials as efficient packing,a series of dielectric elastomer composite material were prepared with good electrodeformation effect.The scalable capacitance sensor was obtained and the relationship between tension and output capacitance was studied.The application fields of dielectric elastomers were further extended.The main work of this paper has the following seven aspects:(1)In this paper,submicron and micron calcium copper titanate(CCTO)crystallites with different morphologies were successfully designed and prepared by directly thermal treatment method and molten salt method,respectively.Thern,the silicone elastomer filled with self-prepared CCTO particles had high dieletric constant,low dielectric loss,and actuated strain which was greatly improved at low electric field.The dieletric constant at 50 Hz obviously increased from 2.15 for pure silicone elastomer to 4.37 and 4.18 for the submicron and micron CCTO/poly(dimethyl siloxane)(PDMS)composites.The dielectric loss of the composites retained at a low value(less than 0.06).Meanwhile,the elastic modulus of CCTO/PDMS composites was only increased slightly.And the CCTO/PDMS composites still had a good flexibility.Compared to pure silicone elastomer(2.25%),the submicron and micron CCTO/PDMS composites with 2 wt.%content exhibited a greater strain of 7.69%and 9.83%at a low electric field of 5 V/μm.(2)In this paper,core-shell structured calcium copper titanate@polyaniline(CCTO@PANI)was synthesized using a simple procedure involving in-situ polymerization of aniline in aqueous hydrochloric acid solution.Then,the silicone elastomer filled with self-prepared CCTO@PANI composites had high dieletric constant,low dielectric loss,and actuated strain which was greatly improved at low electric field.Meanwhile,the elastic modulus of CCTO@PANI/PDMS composites was only increased slightly.And the CCTO@PANI/PDMS composites still had a good flexibility.Compared to pure silicone elastomer(8.94%),the CCTO/PDMS and CCTO@PANI/PDMS(The weight ratio of CCTO and aniline was 10)composites exhibited a greater actuated strain of 10.95%and 13.24%at a low electric field of 10 V/μm and filling content,respectively.This study provided a simple and effective method for the improvement of actuated strain at low electric field through preparation of CCTO@PANI/PDMS composites due to the hyper-electronic polarization and a strong polaron delocalization,facilitating the wide application of dielectric materials.(3)In this paper,polypropylene glycol diacetate(PPGDA)with different molecular weight was obtained by the esterification reaction of polypropylene glycol and acetic anhydride.It can reduce effectively the residual moisture and hydrophilicity of PPGDA.Then,polydimethyl siloxane(PDMS)was modified by addition of only 5 wt.%PPGDA,which possessed high dieletric constant(k)and large actuated strain at low electric field.PPGDA was employed to enhance the molecular polarity due to more polar oxygen atoms and produced more ester groups.The great increase in k and low elastic modulus of PPGDA/PDMS composites lead to the great increase in electromechanical sensitivity(β).When the molecular weight of PPGDA was about 4000,PPGDA/PDMS composites had the largest actuated strain.As a result,compared to pure silicone elastomer(8.94%),it exhibited a greater strain of 17.31%at a low electric field of 10.5 V/μm(about 1.94 times increase).(4)In this paper,we report an effective method for the preparation of silicone dielectric elastomers(PDMS)containing only 0.5 wt.%π-conjugated truxene micromolecule.The as-prepared truxene/PDMS composite had high dieletric constant(k)due to the regularly rigid structures,special π-conjugated structure and monodisperse nature of truxene,which can form a large number of parallel micro-capacitors under actuated electric field.In addition,the elastic modulus of truxene/PDMS composite was only increased slightly.And the truxene/PDMS composites still had a good flexibility.As a result,compared to pure silicone elastomer(4.52%),the truxene/PDMS composite exhibited a greater strain of 11.56%at a low electric field of 5.5 V/μm(about 2.56 times increase).(5)In this paper,the partly conjugated polymer/silicone dielectric elastomers(PCP/PDMS)were obtained at higher temperature such as 180℃ via in-situ dehydrochlorination reaction of PVC(polyvinyl chloride)/PDMS.The as-prepared PCP/PDMS composites had high dieletric constant(k),low dielectric loss,and high actuated strain which was greatly improved at a low electric field.The great increase in k and low elastic modulus of PCP/PDMS composites lead to the great increase in electromechanical sensitivity(β).As a result,compared to pure silicone elastomer,the 2.81 times increase in(3 at 50 Hz and 1.96 times increase in actuated strain at a low electric field(10 V/μm)were achieved by adding only 1 wt.%PVC.(6)Multi walled carbon nanotubes(MWCNTs)with smaller aspect ratio were prepared by repeated cyclic shearing of MWCNTs.The dieletric constant at 50 Hz obviously increased from 2.15 for pure silicone elastomer to 4.38 for the MWCNTs/PDMS composites filled with 0.0125 wt%MWCNTs.The addition of MWCNTs had little effect on the modulus of the composite elastomer.As a result,compared to pure silicone elastomer,MWCNTs/PDMS composite exhibited a greater strain of 17.61%at a low electric field of 9 V/μm(about 2.07 times increase).(7)The soluble conductive polyaniline material was synthesized by emulsion polymerization with dodecylbenzenesulphonic acid as doping organic acid and emulsifier,and toluenen as solvent.Then,polyaniline/SEBS composites were prepared by volatilization of homogeneous solvent.The dielectric elastomer and flexible electrode were prepared with different dosage adjustment of polyaniline,which was easy to paste due to the homogeneous materials.The flexible capacitance sensor was obtained by dielectric layer with the filling amount of 2 wt%PANI/SEBS and conductive layer with 25 wt%quantity of PANI/SEBS.The relationship between the tensile-capacitance preliminary was studied by the precision LCR meter capacitance test with stable signal,which is consistent with classical capacitance theory.