Abstract: In order to study the hydrothermal aging characteristics of glass fiber reinforced unsaturated polyester resin fire barrier, the equivalent hydrothermal aging treatment of fire barrier was carried out in combination with the actual temperature and humidity environment and accelerated aging model in cable tunnel. The microstructure, thermal stability, combustion performance and mechanical properties of the samples were tested by scanning electron microscopy, thermogravimetric test, oxygen index test and impact strength test. The results show that white powder precipitates on the surface of the sample after 1 cycle of aging, and obvious cracks appear on the section after 3 cycles of aging. The microstructure diagram shows that the resin in the sample falls off from the glass fiber after 2 cycles of aging, and a large amount of glass fiber is exposed after 5 cycles of aging. The peak mass loss rate of the sample eventually increased by 45%. The impact strength finally decreased by 41.6%. The bending strength finally decreased by 47.3%. The bending strength of water absorption finally decreased by 42.5%. It shows that the thermal stability and mechanical properties of the samples decreased significantly after hygrothermal aging. The oxygen index of the sample was finally increased by 28.7%. The smoke density meets the technical specifications. The above two tests cannot be used as an indicator to judge the performance degradation of the fire barrier after hygrothermal aging.

Key words: glass fiber, resin matrix composites, fire partition board, damp heat aging, thermogravimetric analysis, scanning electron microscope