Abstract: In this paper, aramid Ⅲ paper base paper was obtained by wet forming with aramid Ⅲ staple fiber and meta-aramid fibrid, and then the aramid Ⅲ paper base composite was obtained by impregnating polyimide resin, and then the aging experiments were carried out at 250 ℃, 300 ℃ and 350 ℃. The physicochemical structure, mechanical properties and dynamic mechanical properties of Fang Ⅲ paper before and after aging were described. The results show that the chemical structure of aryl Ⅲ paper has no obvious change before and after aging at 250 ℃ and 300 ℃, and the amide bond breaks before and after aging at 350 ℃. For the physical structure of paper, with the increase of aging time and aging temperature, the quality loss and size loss of aromatic Ⅲ paper gradually become larger, and the paper surface defects such as holes and cracks appear. After aging at 250 ℃ for 408 h, the tensile strength and tear strength retention rates of Fang Ⅲ paper were 111% and 115%, respectively. After 312 h aging at 300 ℃, the tensile strength and tear retention rate of aromatic Ⅲ paper decreased to 53% and 23%, respectively. After aging at 350 ℃ for 168 h, the tensile strength retention rate of aromatic Ⅲ paper was only 4%, the tear retention rate decreased to 14% after aging for 48 h, and decreased to 0 after 168 h. DMA shows that the loss factor transition temperature of aromatic Ⅲ paper increases gradually with the increase of aging time at 300 ℃, indicating that the molecular segment softness and viscosity of aromatic Ⅲ paper increase significantly at 300 ℃.

Key words: aramid Ⅲ staple fiber, aramid Ⅲ paper base paper, paper base composite, thermal and oxidative aging, mechanical properties