In order to study the influence of nanoparticles on the insulation performance of polyimide film after damp

taking polyimide（PI） Film and polyimide nano-film as test objects

we performed the corona tests

the breakdown field strength tests

and dielectric loss tests on the film before and after water absorption. Fourier transform infrared spectroscopy（FTIR） was used to study the chemical structure changes under the different proportion of water absorption. The results show that

with the increase of water absorption

the dielectric loss will increase

and the corona resistant time of pure PI film and nanocomposite PI film will increase first and then decrease. The breakdown field strength of PI film will tend to gradually drop with the increase of water absorption. The FTIR images reveal that

in the presence of water

the imide ring opening reaction takes place

generating many short molecular chain and some ionic groups of compounds. On the one hand

the increased number of carriers speeds up the charge dissipation

inhibiting the accumulation of local charge; on the other hand

the absorption of water increases the dielectric loss and weakens the dielectric properties

degrading the film insulation performance. Because the "water shell" may be formed around the nanoparticles from water molecules

the transmission channel of the charge will increase in the nanocomposite PI films. The tendency of nanocomposite PI film’s corona resistant time which increases first and then decreases is more obvious. At the same time

the hydrolysis reaction with the water molecules and the molecular chain of PI break the chemical bonds between nanoparticles and PI molecular chain

reducing the stability of the polymer matrix. Therefore

the breakdown strength of nanocomposite PI film drops seriously.