Preparation And Energy Storage Properties Of High Dieletric Aromatic Polyurea Films

With the development of modern technology,the circuit has broad application prospects in modern electronic devices and power systems（such as medical equipment,hybrid electric vehicles（HEVs）,filters,switching power supplies and power weapon systems）;Polyurea has attracted people’s attention due to its small open circuit failure,light weight,high breakdown strength,good compatibility with organic substrates or printed circuit boards,and other characteristics.In this paper,we prepared two kinds of polyurea with different structures and then doping modification of ceramic nanoparticles and conductor materials with polyurea film as the matrix,the dielectric constant of the matrix polymer is further improved.Using the impedance value at normal temperature,the applied electric field strength and the D-E loops under different electric fields to analyze the dielectric and energy storage performance of the samples.In this paper,the ArPU Ⅰ polyurea films were prepared by solution polymerization method,using MDA and MDI though controlling different reaction conditions and isocyanate index（R）.When R is 1.06,the polymerization proceeds most fully and the performance is optimal in all aspects.At this time,the dielectric constant of ArPU Ⅰ can be stabilized at 5.89 when the frequency is greater than 103 Hz.Based on this,m PDA was introduced into the structure,and its molar fraction was controlled to be 0 % ～ 50 % of the diamine ratio,and the gradient was increased by 10 % to prepare ArPU Ⅱ series films with higher dipole density;Among them,ArPU Ⅱ-20 %,on the basis of maintaining good mechanical and thermal stability,the breakdown field strength can reach 516 MV/m,and the highest energy storage density is 6.65 J/cm³.PDA@MWCNTs/ArPU Ⅱ composite film was prepared with ArPU Ⅱ-20 % as the matrix and doped with PDA@MWCNTs with a mass fraction of 0 % ～ 1.5 %;The sol-gel method was used to prepare barium titanate nanoparticles,and a BT / ArPU Ⅱ composite film with a BT-HN₂ doped mass fraction of 0 % ～ 25 % was obtained by insitu blending.When the mass fraction of PDA@MWCNTs is 1.25 %,the dielectric constant of the film is close to 11,which is about 2 times the dielectric constant of the base film.As the MWCNTs increases,the breakdown field strength of the film decreases.The addition of BT will reduce the mechanical properties of the film,but the dielectric constant will continue to increase.When 10 % BT is added at room temperature,the dielectric constant of the composite film can reach about 8,but the dielectric loss is obvious at high frequencies.The effective energy storage density of BT/ArPU II-5 % under 500 MV/m electric field reaches 7 J/cm³.The series of films prepared in this paper all have good mechanical properties and good thermal stability.They can be used in high temperature environments（200 °C）.The addition of fillers will increase the thermal decomposition temperature of the base film,thereby expanding the use of the composite film.