Synergistic Broadband Acoustic Absorption of M‐C/ <scp>CPPC</scp> / <scp>PU</scp> Foam Composites via Cell Size and Compressive Modulus Regulation

ABSTRACT Foam materials are widely used for acoustic absorption due to their light weight, high porosity, and energy absorption. Conventional foams exhibit limited mid‐high frequency sound absorption, linked to their cellular structure, and matrix toughness. This paper introduces mesoporous ceramic (M‐C) and chlorinated poly(propylene carbonate) (CPPC) into polyurethane (PU) foam to fabricate M‐C/CPPC/PU foam composites with a nano‐micro hierarchical cellular structure through physically confined foaming. M‐C acted as a heterogeneous nucleating agent, refining the cellular structure of PU foam with cell sizes below 250 μm, which enhanced multiple reflections and scattering of sound waves within the cellular structure. CPPC enhanced interfacial bonding, facilitating the transfer of sound waves incident on cell walls to M‐C particles with nanoscale open‐cell structures, and further extending sound propagation loss paths within the PU matrix. The M‐C/CPPC/PU foam composites with small cells (cell size of 200–250 μm, extending propagation paths) and elastic‐rigid balance (compressive modulus of 110–120 kPa, promoting penetration) achieved superior acoustic absorption, with an average sound absorption coefficient (ASAC) of 0.851 and 0.965 at 1600 Hz, while maintaining notable thermal insulation properties. This paper significantly improves the broadband acoustic absorption (1000–5000 Hz) of foam materials, providing a technical foundation for effective environmental noise control.