Hygrothermal ageing characterisation of epoxy resin based on transmission characteristics of microwave resonator with interdigital‐capacitor‐shaped defected ground structure

Abstract

In this article, a method is proposed for the characterisation of epoxy resin thermal and hygrothermal ageing based on microwave resonator with interdigital‐capacitor‐shaped defected ground structure (IDCS‐DGS), which can realise rapid and simple non‐destructive testing of the ageing degree of epoxy resin materials. The resonant frequency of IDCS‐DGS was proved to decrease with the increase of dielectric constant of the around material by means of simulation. The breakdown test at high voltage showed the deterioration of epoxy resin after hygrothermal ageing, which is caused by moisture absorption and hydrolysis process. In addition, thermal ageing also caused a decline in the insulation performance of epoxy resin samples. Accelerated oxidation of epoxy resin samples at high temperatures produces polar molecules that increase the dielectric constant of the samples. As for the hygrothermal ageing samples, the entrance of polar water molecules will increase the dielectric constant of epoxy resin, and thus make an effect on the resonant frequency of IDCS‐DGS. The tests of transmission performance show that after the hygrothermally aged epoxy resin samples were put on the microwave sensor, the resonant frequency decreased continuously with hygrothermal ageing time, and the deviations of resonant frequency are highly consistent with the weight variation rate of the samples.

Aging Characterization of Modified Insulating Paper Based on the Transmission Characteristics of Microstrip Resonant Sensors

“…CSRR and IDCS-DGS sensors are widely used in the detection field because of their high sensitivity, and have been studied in the aging characterization of traditional electrical insulation materials [23,24]. In this paper, CSRR and IDCS-DGS sensors are further applied to the thermal aging characterization of modified insulating paper.…”

“…More detailed analysis of this structure was carried out by Xiao et al [23]. Figure 4b shows the IDCS-DGS sensor and its IDCS-DGS etched structure [24]. The overall layout is similar to that of the CSRR sensor, and the resonant frequency can also be adjusted by changing the size of the IDCS.…”

“…Based on this method, the complementary split ring resonator (CSRR) was successfully used to detect the presence of water trees inside LDPE samples, and it was also found that the circular CSRR was more sensitive to the presence of water trees than the rectangular CSRR [23]. The interdigital-capacitor-shaped defected ground structure resonator (IDCS-DGS) was used to easily characterize the degree of hygrothermal aging of the epoxy resin and accelerated the analysis process compared to conventional methods [24]. In this paper, the method was also used to characterize the degree of aging of the modified insulating paper.…”

Understanding Water Diffusion Behaviors in Epoxy Resin through Molecular Simulations and Experiments

“…The epoxy resin encapsulated products are inevitably invaded by moisture or water during long-term service, leading to the deterioration of the epoxy resin insulation materials. On the one hand, water absorption can cause deterioration of dielectric properties, a decrease in breakdown strength, , and acceleration of electric tree growth, resulting in a loss of insulation performance . On the other hand, water absorption can also reduce glass transition temperature, diminish stiffness and strength, and even form some microcracks, contributing to a loss of mechanical performance.…”