| Epoxy is one kind of thermosetting resins with comprehensive performance.It has been widely used in electronics, electrical, aerospace, chemicals,electronics packaging and many other fields due to its outstanding properties.However, with the sharp development of the information, more and moreelectronic devices become smaller, lighter, higher output power. Many propertiesof epoxy should be improved so as to satisfy these circumstances.In this thesis, Al2O3nanosheets and Al2O3nanofibers were used to modifybisphenol A type epoxy and prepare Al2O3/epoxy composites with differentAl2O3morphologies. Effects of the nano-Al2O3morphologies on thermal stability,dielectric properties and mechanical properties of Al2O3/epoxy composites werediscussed. First of all, under the certain pH value, Al2O3nanosheets and Al2O3nanofibers were prepared by hydrothermal process. Then, the modified Al2O3nanofibers and Al2O3nanosheets by silane coupling agent were doped into epoxyresin to prepare Al2O3/epoxy composites with different Al2O3morphologies. Themorphylogies and structure of Al2O3were characterized. Meanwhile dielectricproperties, thermal stability, mechanical properties of Al2O3/epoxy compositeswere characterized.The experimental results showed that dielectric strength and volumeresistivity of Al2O3/epoxy composites were improved obviously since the addingof the Al2O3nanofibers and Al2O3nanosheets. Dielectric strength of theAl2O3/epoxy composites with Al2O3nanosheets at the content of7wt%was29.58kV/mm, dielectric strength of the Al2O3/epoxy composites with Al2O3nanofibers at the content of3wt%was29.07kV/mm. Volume resistivity ofAl2O3/epoxy composites with different morphylogies reached maximum at the Al2O3content of5wt%. Volume resistivity of the Al2O3/epoxy with Al2O3nanosheets at the content of5wt%was8.5×1016·cm, which was the2.72timesof neat epoxy (3.12×1016·cm), meanwhile the volume resistivity of theAl2O3/epoxy composites with Al2O3nanofibers at the content of5wt%was5.0×1016·cm, lower than that of the Al2O3/epoxy composites with Al2O3nanosheets. Dielectric permittivity of Al2O3/epoxy composites increased slightlydue to the addition of different Al2O3morphologies, while the morphology ofAl2O3has no obviously effect on dielectric loss of the Al2O3/epoxy composites.Thermal stability of the Al2O3/epoxy composites was enhanced due to addition ofthe modified Al2O3nanosheets. Impact strength and bending strength of theAl2O3/epoxy composites were improved obviously since the adding of the Al2O3nanofibers and Al2O3nanosheets. |
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