Abstract:

γ-Methacryloyloxypropyltrimethoxysilane （KH570） was selected as the silane coupling agent to prepare graphite/polyimide composites with different proportions of coupling agent KH570. The morphology, mechanical properties and thermal stability parameters of the composite system were tested and analyzed. The results showed that all the polyimide composites doped with graphite with different dosages of coupling agent KH570 exhibited the structure of polyimide. The shear strength of the composite adhesive first increased and then decreased with the increase of the dosage of coupling agent, among which the composite system with 5% coupling agent had the highest shear strength of 27.93 MPa. The higher the amount of coupling agent doping, the higher the dielectric constant and the lower the dielectric loss for the graphite/polyimide composite. In the investigated range, the dielectric constant of graphite/polyimide composite reached a maximum of 12.1 at the coupling agent content of 7%, while the minimum dielectric loss of 0.018 appeared at 5% coupling agent doping in the graphite/polyimide composite. The coupling agent improved the interface uniformity of the composite system, as well as the dielectric properties and the thermal stability thereof. The glass transition temperatures of all composite adhesives were around 261 ℃.

Key words: silane coupling agent, KH570, polyimide, mechanical property, dielectric property