Study on Enhancing Low-Frequency Sound Absorption Performance of Polyurethane by Tert-Butanol-Regulated Pore Structure of Cellulose Aerogel Microspheres

Polyurethane foam is widely used for sound absorption due to its mechanical properties and damping performance, but suffers from poor low-frequency noise absorption. To enhance this, this study systematically regulated the pore structure of cellulose aerogel microspheres by controlling the type and concentration of the solvent exchange medium (tert-butanol/water solutions). A composite sound-absorbing material was then fabricated, exhibiting superior low-frequency acoustic performance. The microscopic morphology and pore characteristics of the CA microspheres were investigated, and their pore structure’s influence on CA/PU properties was analyzed to establish a structure–property relationship. Results show that increasing tert-butanol concentration accelerated solvent crystallization and reduced crystal grain size, yielding CA microspheres with smaller pore sizes, higher porosity, lower density and larger specific surface areas. CA microspheres prepared with 50 wt.% tert-butanol exhibited a specific surface area of 61.40[Formula: see text]m 2 /g, an average pore diameter of 14.04[Formula: see text]nm, a bulk density of 0.059[Formula: see text]g/cm 3 , and a narrow particle size distribution and average diameter 202.0[Formula: see text][Formula: see text]m, classifying them as mesoporous materials. Integrating these finely porous CA microspheres with the macroporous PU foam formed a composite structure with high tortuosity and large specific surface area. This composite demonstrated superior comprehensive sound absorption performance compared to pure PU foam or standalone cellulose aerogel, particularly at low frequencies. The findings provide novel technical support for practical noise control applications in daily life.