Polyacrylonitrile nanofiber reinforced polyimide composite aerogels with fiber-pore interpenetrating structures for sound absorption, air filtration and thermal insulation

Prolonged noise pollution and its induced vibration would not only lead to the failure of instruments and equipment, but also endanger human health. In this work, with water-soluble polyamide acid (PAA) as the matrix and polyacrylonitrile nanofiber (PANNF) as the reinforcement, PANNF reinforced polyimide (PANNF/PI) composite aerogels with fiber-pore interpenetrating structures are fabricated by the method of "homogeneous mixing, freeze-drying and heat treatment". PANNF that intersperses among pores can effectively inhibit the shrinkage of PI aerogels and enhance sound absorption and mechanical properties. With PANNF dosage of 10 wt %, the composite aerogels own the excellent sound absorption performance, with noise reduction coefficient (NRC) of 0.398, and average sound absorption coefficient (SAC) of 0.913 in the frequency range of 2000 similar to 6300 Hz. The composite aerogels also have excellent mechanical properties, with Young's modulus of 12.42 kPa, stress loss of 3.64% and energy loss coefficient of 0.203. 10 wt% PANNF/PI composite aerogels also possess satisfying air filtration performance (97.2% filtration efficiency for PM2.5, quality factor (QF) value of 0.0396 Pa-1; and 99.4% filtration efficiency for PM10, QF value of 0.0567 Pa-1) and thermal insulation performance (thermal conductivity coefficient as low as 0.036 W/(m center dot K)).