Chitin/Chitosan Biocomposite Foams with Chitins from Different Organisms for Sound Absorption

Foams are widely used for applications in construction, energy absorption, and building insulation. We developed sustainable chitin/chitosan-based foams derived from snow crab and Aspergillus niger (α-chitin) and from squid (β-chitin), which were obtained via a "shake and bake" process. The foam structure, mechanical, thermophysical, sound absorption, and flammability properties were studied. Stable foams were obtained from snow crab and squid chitin, whereas A.niger-based foams were inhomogeneous. Foams derived from the former biomass sources displayed densities of 0.07–0.30 g/cm3 and bulk porosities of 78–94% with only a minimal number of closed pores. According to mercury porosimetry (MP) and X-ray computed microtomography (μXRCT), pore sizes ranged from 3 μm to 1.5 mm, with the majority of pores being larger than 400 μm. In mechanical compression tests, β-chitin-based foams showed higher specific compressive strength and modulus (up to σ0.1* = 9.00 MPa/E* = 107.37 MPa) compared to the α-chitin-based series. Dynamic vapor sorption (DVS) measurements revealed that the β-chitin (from squid) series overall took up more water vapor (≤40 wt %) than the α-chitin (from snow crab) series (≤33 wt %). Flammability tests showed that the developed foams were suitable for fire protection class E, superior to common polyurethane (PU) foams, and sound absorption tests showed promising results for applications only little influenced by humidity.