Preparation And Properties Of Boron Nitride/Polyimide Films

Boron nitride is a wide band-gap material with good mechanical properties and chemical stability.At the same time,because it has a strong neutron absorption capability,it is also widely appreciated in anti-radiation materials.However,when boron nitride is introduced into a high molecular polymer,Boron nitride is poorly dispersed in the organic polymer due to a weak interaction force in the inorganic-organic mixture,and the prepared composite materials has uneven surface and poor mechanical properties.The current research trend is to modify the surface of boron nitride so that it has organic groups that can chemically bond with organic polymers.Polyimide is a widely used polymer material with good thermal,mechanical,electrical properties and radiation resistance,and can be used as a matrix for preparation of radiation resistant composites.A novel boron nitride and polyimide composite method is provided herein:Boron nitride is prepared by modifying boron nitride with different silane coupling agents to improve the solubility of boron nitride/Polyimide composite material in a polyimide matrix.On this basis,in order to meet the requirements of high-energy electron irradiation,nano Pb was introduced to prepare sandwich structure three-layer polyimide composites?PI/PI?Pb?/PI?with a thickness of 1.0 mm and five layers of polyimide.Composite materials?PI/PI?MWNT-NH₂?/PI?Pb?/PI?MWNT-NH₂?/PI?.The specific research content is as follows:1.Prepare different silane coupling surface modified BN.In this thesis,the combination of boron nitride?BN?and PI material was selected.The surface modification of BN with methyltriethoxysilane and?-aminopropyltriethoxysilane coupling agent?KH550?were performed respectively,and the modification methods with good performance were selected to prepare them using the thermal imine method and coating process.Doped Surface-Modified Boron Nitride?FBN?Polyimide Composite PI?FBN?.2.Prepare a sandwich structure PI?Pb?composite material with sufficient thickness.Direct film formation,solvent extraction formation,thick film formation,and glass film formation to prepare the thickness greater than 1.0mm PI?Pb?ionizing radiation composite.3.Performance testing and related structural characterization.In this dissertation,Fourier transform infrared FTIR,energy spectrum EDS and other instruments wereusedtocharacterizethesynthesizedcompoundsand surface-modified boron nitride.⁶⁰Co was applied to pure PI and the composite material PI?FBN?.Irradiation of?-rays from radiation sources;mechanical properties of irradiated PI?FBN?samples were tested using an electronic multi-purpose tensile tester;thermal stability was measured using a thermogravimetric analyzer TGA;electrical properties spectrometer was tested by the dielectric impedance spectrometer;finally,an electron accelerator was used to study the shielding properties of the material against ionizing radiation.The experimental results show that the polyimide composite material prepared by surface modification of boron nitride with methyltriethoxysilane has better film formation,and the PI?FBN?material prepared by using PI as a reference has a high?against ⁶⁰Co.The radiation has certain radiation resistance,but the effect is not obvious.In addition,the pre-cured film-forming process sandwich structure three-layer polyimide composite material has a certain shielding effect for high-energy electron radiation.