Hierarchical porous bio-composites derived from durian peel fiber: From matrix-encapsulated to congested networks for advanced acoustic attenuation.

Valorization of agricultural residues addresses dual sustainability challenges: waste reduction and petroleum alternative development. This study demonstrates processing-controlled synthesis of acoustically functional bio-composites from durian peel fiber (DPF) combined with cassava starch binder. Composites were prepared at six DPF loadings (10-60 wt%) and evaluated for porosity, acoustic attenuation, physical, flexural, and thermal properties, moisture resistance, and biodegradability. Increasing fiber content produced a morphological transition from matrix-encapsulated (CDF10) to DPF-network-dominated appearance (CDF60) in SEM cross-sections, accompanied by increased porosity (17 to 49%), decreased bulk density (1.18 to 1.01 g cm-3), and reduced hydrophilicity. The composites showed formulation-dependent modulation of relative sound transmission loss (rSTL) spectrum measured in the custom two-cavity apparatus. The rSTL spectra contained several sharp peaks with formulation-dependent relative amplitudes. The highest peak of CDF60 appeared at 1500 Hz (40 dB) while the highest peak of CDF10 appeared at 4160 Hz (34 dB). Flexural modulus increased with fiber loading (180-351 MPa). Thermal analysis revealed DSC onset degradation temperatures at 244-247 °C and TGA initial mass loss at 240-229 °C, with main degradation peaks at 295-308 °C and 17-22% char formation. Preliminary soil-burial studies (8 weeks, pH 6.4, 25 °C, ≥60% moisture) confirmed progressive apparent mass loss (44-88%), highlighting the susceptibility to environmental degradation under these specific soil conditions. These findings establish DPF/cassava starch composites as promising, sustainably sourced candidates for development as acoustic panel materials. Standardized acoustic testing, long-term durability evaluation, and fire-performance characterization remain necessary before regulatory acceptance in building applications.