Influence of ultraviolet irradiation on dielectric properties of polyetherimide film

The effect of ultraviolet irradiation on the dielectric properties of polyetherimide (PEI) film samples was investigated. FT-IR and SEM were used to characterize the molecular structure and the surface morphology of the untreated and treated PEI films in different UV irradiation time. The results show that the absorption peak of the irradiated PEI film at 1724 cm-1 was greater than that of the virgin, which indicates the amount of C=O groups increases with increasing irradiation time, and cracks occurred on the PEI surface. The dielectric properties of PEI films were also studied in detail. The results show that, with the increase of irradiation time, the relative dielectric constant and the dielectric dissipation factor increased, surface resistivity decreased, and volume resistivity was almost unchanged. PEI film of DC breakdown strength firstly increased, and then decreased with the increase of radiation time. Moreover, the irradiated films breakdown strengh at a certain irradiation dose is 20% greater than that of the original film, which may be attributed to the crosslinking action under the ultraviolet irradiation.