Preparation And Research Of Electromagnetic Protection Materials Based On Polyimide And MXene

The rapid development of 5G communication and microelectronics technology brings convenience to people’s life but also serious electromagnetic interference pollution,so it is crucial to prepare high-performance electromagnetic protection materials.Compared with traditional metal materials,polymer composites have become more promising alternatives in the field of electromagnetic protection materials because of their corrosion resistance,high specific strength,low cost,and easy processing.Polyimide(PI)has excellent heat resistance,high and low-temperature resistance,and good mechanical strength,and is often used to prepare electromagnetic protection materials.In this thesis,PI is used as the polymer matrix to prepare electromagnetic protection materials by adding MXene,carboxylated carbon nanotubes(CCNT),and short-cut carbon fibers(CF)to explore the effect of filler addition on the comprehensive performance of composite materials,to expect to obtain comprehensive performance of excellent electromagnetic protection materials.The details of the study are as follows:1.MXene was obtained by chemical etching,and large-size MXene/PI composite films were prepared by a simple scratch method and thermal imidization method.Then the effect of MXene content on the mechanical properties,microscopic morphology,electrical conductivity,and electromagnetic interference shielding effectiveness(EMI SE)of the composite films were investigated.The results show that the introduction of MXene gives good EMI SE and conductivity to the composite films,and the EMI SE and conductivity of the composite films increases with the increase of MXene content.When the MXene content is 25 wt%,the composite film exhibits an EMI SE of 29.12 d B and a specific EMI SE of 208 d B/mm(SE/thickness),as well as a conductivity of 0.0526 S/cm.2.MXene/CCNT/PI composite films were synthesized by scratch method and thermal imidization,and the synergistic effect of MXene and CCNT imparted high electrical conductivity to the films,thus achieving efficient electromagnetic shielding.The results show that the composite films have excellent EMI SE,and the films possess durable and stable EMI SE under extremely harsh environments.When the content of the MXene and CCNT both is12.5 wt%,the film(thickness of 80 μm)has 26.49 d B EMI SE and 331.13 d B/mm specific EMI SE,and the conductivity is 5.88 S/cm.Moreover,the EMI SE is almost constant after acid/alkaline treatment,high and low-temperature treatment,and repeated bending,and has stable electromagnetic shielding performance.3.MXene/CF/PI composite aerogels were constructed by the freeze-drying method.By introducing CF to the aerogels for skeleton reinforcement and limiting the shrinkage generated of PI aerogel during imidization,multifunctional composite aerogels with wave absorption properties,flame retardant and thermal insulation properties,and excellent mechanical properties were obtained.The results show that the microwave absorption capacity of the composite aerogels is significantly improved with the increase of MXene and CF content.When the MXene content is 24 wt% and CF addition is 6 wt%,the minimum reflection loss of the aerogel(thickness of 3.3 mm)reached-61.96 d B and the effective absorption bandwidth is 3.97 GHz.