In order to explore the aging characteristics of room temperature vulcanized silicone rubber（RTV） insulation protective material in the environment with conditions of variable temperature and large temperature difference between day and night

RTV samples were prepared and the thermal-cooling cycle aging simulation tests were conducted in this paper.The change laws of microstructure characteristics before and after aging and aging mechanism were studied through Fourier infrared spectroscopy（FTIR） and scanning electron microscopy（SEM）.The tensile test

dielectric properties test and breakdown test were conducted to analyze the change laws of macro characteristi-s

such as mechanical properties

volume resistivity

dielectric properties

and breakdown strength during the thermal-cooling cycle aging process.The results showed that the molecular chain cross-linking network of samples deteriorated during the thermal-cooling cycle aging process

and strong polar groups（such as-OH） were generated at the same time.Under the combined effect of aging temperature and temperature stress

the phenomenon of filler shedding

formation of holes and cracks appeared on the near surface of the sample

and the microstructure was destroyed to a certain extent

resulting in decreased mechanical properties

reduced volume resistivity

increased relative permittivity and dielectric loss

and decreased breakdown strength.In general

overall insulation performance deteriorated.