Focused on liquid silicone rubber（LSR）sheds of high-voltage DC bushing operated in South China

this paper analyzed the microscopic characteristics of the sheds’chalking layer and inner layer

using techniques such as scanning electron microscope（SEM）

Fourier Transform Infrared Spectroscopy（FTIR）

X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）.SEM graphs show that the chalking layer’s micro-surface changes into irregularly shaped patches with a decrease of adhesion.FTIR

XRD and XPS results indicate that in the chalking layer

the side chain groups of polydimethylsiloxane（PDMS）are oxidized

and cross-linked with other siloxane chains

forming more Si-O-Si groups.Furthermore

the precipitation ofcarbon-white is found in chalking layer.According to the aging behavior of LSR

this paper extracts several characteristic variables to for qualitative aging status evaluation of LSR:the ratio of absorption peaks relevant to Si-O-Si and Si-C chemical bonds in FTIR;the ratio of diffraction peaks relevant to amorphous silica and PDMS in XRD;the average atomic ratios of Si/O/C in siloxane chain units obtained from peak fitting of Si 2p spectrum in XPS

etc.Comparing these characteristic variables of LSR samples’inner and surface layer would help to evaluate the aging status more accurately.