Maximizing sound absorption, thermal insulation, and mechanical strength of anisotropic pectin cryogels

Effective use of sound absorption materials is the main way to reduce noise pollution, which constitutes a major environmental and health problem. However, the currently used porous sound absorption materials cause not only environmental pollution but their usage is also a potential health risk. Here, we demonstrate a facile strategy to create environmental-friendly and non-toxic lightweight pectin-based cryogels with hierarchically porous anisotropic structure, which integrates small pores on the walls of lamellar pores, via freeze-casting method. The fabricated pectin cryogels have better sound absorption performance (average sound absorption coefficient up to 0.76 in 500–6000 Hz), higher compression modulus (300 to 700 times higher than commercial glass wool), and comparable thermal conductivity comparing to other reported bio-based porous materials. Moreover, the sound absorption performance could be enhanced and optimized by tuning the pore wall density of lamellar pores and the size of small pores to the level of viscous and thermal layers via increasing of freeze-casting temperature and adding NaCl in pectin solution prior to the freeze-casting process. The outstanding sound absorption is linked to the unique hierarchically porous morphology of these cryogels. This strategy paves the way for the design of bio-based porous anisotropic materials for highly efficient noise absorption.