| Dielectric elastomer materials(DEs)are a type of intelligent composite materials that can quickly convert electrical energy into mechanical energy under external electric field.Due to its characteristics of electro-deformation,short response time and reusable use,DEs has wide application prospects in the fields of variant robots,aerospace vehicles,electric drives and smart wearables.At present,the biggest challenge of DEs has to face involving low intrinsic dielectric constant and excessively high driving electric field(greater than 25 V/μm),which increases its limitations in practical applications.Therefore,how to achieve high electro-induced deformation at low voltage has become the research highlight and difficulty of dielectric elastomer materials.According to the theoretical model of dielectric elastomer drive,increasing the dielectric constant of the material is a key factor for achieving high-performance dielectric elastomer materials,while reducing its elastic modulus while meeting application requirements.The main research contents of this paper are as follows.1."Sandwich" structure graphene composite polyurethane dielectric elastic materials.Graphene oxide was prepared by the classic Hummers method,which was composed of titanium dioxide(TiO2)with good hydrophilicity,and a high dielectric constant "sandwich" structure graphene/TiO2/graphene inorganic composite filler was prepared.It is casted with thermoplastic polyurethane(TPU)to form a film to obtain a graphene/titanium dioxide-polyurethane(rGO/TiO2-TPU)dielectric elastomer composite material with an isolation structure,and the corresponding electrical conductivity is less than 10-8 S·m-1.The new filler can enhance the dielectric constant of the dielectric elastomer and at the same time make the composite material have a high sensitivity to electro-deformation,achieving 2.9%electro-deformation at a low electric field(15 V/μm).2.Graphene-encapsulated carbon nanosphere composite polyurethane dielectric elastic material.Graphene-encasulated carbon nanospheres(rGO＠CNS)core-shell structure fillers were prepared by hydrothermally combining glucose-derived carbon nanospheres(CNS)with graphene.Scanning electron microscopy and infrared spectroscopy characterization found that the CNS broke the crystallinity of the TPU matrix by breaking the internal hydrogen bonds of the TPU matrix.After the carbon-based CNS filler thermoplastic polyurethane(TPU)is composited into a film,the dielectric constant of the composite material is increased to nearly 30(at 103 Hz)compared to the intrinsic amount of 3 wt%of rGO@CNS,and rGO@CNS/TPU composite material has a low dielectric loss(less than 0.1 at 103 Hz).The prepared dielectric elastomer achieved a maximum electrostriction of 4.9%under a DC electric field of 12 V/μm.3.Polyaniline modified graphene composite polyurethane dielectric elastic material.The polyaniline material is prepared in a low temperature environment and attached to the surface of graphene to obtain a class of organic filler modified graphene dielectric filler.The dielectric material prepared after composing with polyurethane has low dielectric loss and high compatibility at filler content of 5 wt%,which DC electric field of 17 V/μm can achieve a maximum electrostriction of 3.6%. |
