Preparation And Energy Storage Properties Of G-BT/Polyimide Composites

With the development of science and technology,capacitors have been applied more and more in the high temperature environment,which presents a great challenge for the temperature-resistant energy storage dielectric.Polyimide(PI)has been widely concerned for its excellent thermal stability and good insulation.PI has a high dielectric strength and is easy to process,but its dielectric constant is low,only about3.4,which limits its application in the field of dielectric.Improving its dielectric performance through filling modification has become a research hotspot at home and abroad.This paper to design the structure of PI,to introduce oxazole groups,with BZD,BPDA and lab homemade TMBA as reactive monomer,using two-step synthetic PI,synthetic intermediate polyamide acid(PAA)first,and then the gradient temperature,100?,120?,150?,170?,200?,250?,300?,dehydration,get PI.The effect of oxazole content on the dielectric properties of PI was investigated.The PI-3sample with oxazole content of 0.1 has the best performance in all aspects,and its dielectric constant reaches 3.86 at room temperature,higher than other components which is about 3.5.BT and G were introduced into PI-3 as filler phase.In the method of in-situ polymerization,BT modified by silane coupling agent ATPS was firstly filled into it,and after success,G modified by ATPS was continued to be filled,and PI composite dielectric was synthesized by two-step method.It is found that BT is beneficial to mechanical properties,thermal stability and thermal dielectric stability.The existence of BT decreases the sensitivity of PI's dielectric constant to temperature,and the higher the content of BT,the higher the dielectric constant and the lower the dielectric strength.The introduction of G has significantly increased the permittivity of PI.At room temperature,the permittivity of G/PI-2 samples with G content of 1 wt%has reached 10.36,2.68 times higher than that of matrix PI-3.However,its presence will significantly reduce the permittivity of PI.The dielectric loss of the polyimide samples synthesized in this paper was no more than 0.026,lower than the average value in the literature which was 0.04.The dielectric strength of pure PI samples was high,and the dielectric strength of PI-3 at room temperature reached 493.28 MV/m,higher than the average value in the literature which was 300 MV/m.It was found that the permittivity of all PI samples first decreased and then increased with the increase of temperature,reaching the minimum value at 90?.In terms of energy storage,the energy storage of PI-3 at room temperature reaches 1.44 J/cm~3.The dielectric constant increased significantly,the energy storage density increased.The thermal stability of the PI samples synthesized in this paper is very good,and they can work almost lossless at 200?,and the loss amount is very small at about 5%at 500?.