Study On The Preparation And Properties Of Modified Graphene/Carbon Nanotubes/Polyimide Composites

One-dimensional carbon nanotubes and two-dimensional graphenes can modify polyimide resins effectively.Preparing graphene/carbon nanotube/polyimide composites in suitable methods can get synergistic effect among them,so these composites have more excellent thermal performances and mechanical properties.In this paper,we used N,N'-dimethylformamide?DMF?as solvent,polyimide synthesised by 4,4'-diaminodiphenyl ether?ODA?and pyromellitic dianhydride?PMDA?as matrix,graphenes and carbon nanotubes modified by KH-550 as reinforcements.Then we prepared modified graphene/polyimide?KGO/PI?nanocomposites,modified carbon nanotube/polyimide?KCNT/PI?nanocomposites and modified graphene/modified carbon nanotube/polyimide?KGO/KCNT/PI?triple nanocomposites by in-situ polymerization,respectively.Morphology,thermal performances and mechanical properties of the composites were investigated by infrared spectroscopy?IR?,scanning electron microscope?SEM?,differential scanning calorimetry?DSC?,thermogravimetric analysis?TGA?,dynamic echanical analyzer?DMA?and universal testing machine.The SEM showed that KGO and KCNT both dispersed uniformly in polyimide matrix and no obvious phenomenon of agglomeration occurred.KH-550 could prevent graphenes or carbon nanotubes stacking or twining in the matrix.The thermal performances and mechanical properties of the modified KGO/PI nanocomposites were studied.The thermal performances showed that thermal stability,internal friction and modulus increased after adding KGO while the glass transition temperature changed little.When the content of KGO was 0.1%,the decomposition temperature reached the highest value,T_d5%was 559.09?and the starting storage modulus increased 25.91%.The mechanical properties showed that tensile strength and elastic modulus improved with the increase of the content of KGO.When the content of KGO was 0.1%,the mechanical properties were maximum,the tensile strength increased 17.55%and elastic modulus increased 8.68%.The thermal performances and mechanical properties of the modified KCNT/PI nanocomposites were studied.The thermal performances showed that thermal stability,internal friction and modulus also increased after adding KCNT.When the content of KCNT was 0.5%,the decomposition temperature reached the highest value,T_d5%was 563.29?and the starting storage modulus increased 27.74%.The mechanical properties showed that tensile strength and elastic modulus improved after adding KCNT.When the content of KGO was0.5%,the tensile strength increased 10.76%.And when the content of KGO was 1.0%,the elastic modulus increased 12.16%.Adding KGO and KCNT into the polyimide matrix at the same time and getting KGO/KCNT/PI triple nanocomposites.The synergistic effect of KGO and KCNT in the polyimide matrix was studied.The result showed that the three-dimensional structure formed by the two types of nanoparticles made the dispersion effect and combination with matrix best when the ratio of KCNT to KGO was 2 to1.The synergistic effect maximized with T_d5%was563.29?and storage modulus,tensile strength and elastic modulus increased 27.74%,24.71%and 24.28%,respectively.It showed that one-dimensional carbon nanotubes interpenetrated in two-dimensional graphene layers to connect the graphene layers and prevent them from stacking and three-dimensional structure was got,so the contact area and interface binding force of them increased.The thermal performances and mechanical properties improved because the load and energy transmitted effectively to three directions to play a role of synergistic effect.