Characterization And Properties Of Bismaleimide Modified By SiO₂-coated Graphene Composites

Polymer materials have an irreplaceable role in energy storage materials and equipment because of their advantages of low density,easy processing,low price and high breakdown strength.Bismaleimide?BMI?is a resin matrix with high heat resistance temperature and easy processing,which has been widely used in aviation,aerospace,electronics,electrical appliances and other fields in recent years.In order to improve the mechanical properties,dielectric properties and heat resistance of BMI,graphene?GE?is commonly used as a filler to prepare composite materials.In this paper,GE was treated by different methods to improve its dispersion performance in the BMI.Two kinds of silane coupling agents,vinyl-trimethoxysilane?a171?and?-?methacryloyloxy?propyltrimethoxysilane?a174?were used to modify GE to get a171-GE and a174-GE.The mechanism of modification was analyzed.At the same time,Reduced graphene oxide?r GO?had been prepared by oxidation-reduction method.SiO₂was coated on the above three modified GE by Sol-gel method to prepare a171-GE@SiO₂,a174-GE@SiO₂ and r GO@SiO₂,which tetraethyl orthosilicate?TEOS?was used as a silicon source.Fourier transform infrared spectrometer?FT-IR?,scanning electron microscope?SEM?,transmission electron microscope?TEM?and energy dispersive spectrometer?EDS?was used to analyze and compare the coating effects of three kinds of modified GE to explore the coating mechanism,and a171-GE@SiO₂ was chosen as the best solution for the preparation of the following composite material.The matrix of composite?MBAE?was prepared from 4,4'-diaminodiphenyl methane bismaleimide and diallyl bisphenol A?BBA?,bisphenol A bisallyl ether?BBE?and 4,4'-diaminodiphenylmethane bismaleimide?MBMI?,in which BBA and BBE as the reactive diluents.The different content of a171-GE@SiO₂ was used as the filler.The SEM photographs of the fracture of a171-GE@SiO₂/MBAE show that a171-GE@SiO₂ has good dispersion in MBAE.Moreover,the mechanical properties of a171-GE@SiO₂/MBAE composites are significantly improved.The impact strength of composites reaches 23.01k J/m² and the bending strength reaches 157.41 MPa when the content of a171-GE@SiO₂ is 2wt%,which are 150%and 57%higher than that of the MBAE matrix,respectively.The dielectric constant of the composite increases with increasing a171-GE@SiO₂ content,and reaches a maximum of 92 at 2.4 wt%,which is 29 times that of MBAE.The dielectric loss has a small range rise with the increase in the a171-GE@SiO₂ content,but remains below 0.01.The heat resistance of a171-GE@SiO₂/MBAE improves with the increase of a171-GE@SiO₂ content.,The T_d of a171-GE@SiO₂/MBAE reaches a maximum of 429?when the content of a171-GE@SiO₂ is 3wt%.