The importance of this work is the use of waste seashells WSS (5, 10, 15, 20, 25, and 30 wt.%) as a bio-filler to enhance the mechanical and acoustical characteristics of flexible polyurethane foam (FPU). Petroleum-based polyol was partially replaced by 25% castor oil resulting in high renewable content. The WSS was characterized by X-ray photoelectron spectroscopy (XPS). The chemical structure and morphological features for castor oil-based flexible polyurethane waste seashells (CO-FPU-WSS) composites were detected using Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM) techniques, respectively. Besides, the mechanical, non-acoustical and acoustical properties were investigated. The results indicated that bio-based FPU composites possessed better compressive strength than neat FPU foam. In addition, FPU composites enhance the sound absorption below 500 Hz. A 6 cm air gap behind the sample shifted the absorption toward 400 Hz (0.85) for CO-FPU-WSS 25% composite with a broader band. Thus, the FPU foam composite is considered a promising candidate for sound absorption applications such as for the automotive and building industries.

In this work, chitosan (CT) with different ratios (0–5 wt.%) was utilized as a bio filler in polyurethane flexible (PUF) foam to increase mechanical performance and bacterial inhibition characteristics. The chemical structure of CT and polyurethane flexible foam/ chitosan (PUF/CT) composites was examined using FTIR spectroscopy. Furthermore, the cross-link density of PUF/CT composites was examined using the Flory and Rhener equation. Moreover, the PUF/CT composites’ thermal stability was observed utilizing TGA analysis. Further, the morphology and phase behavior of the PUF/CT composites were investigated using SEM and DSC techniques, respectively. The results showed that the cross-link density, thermal stability, cavities sizes, and the glass transition temperature of soft segments Tg(ss) increased with increased CT wt.% content. Besides, characteristics like apparent density, compressive strength, elongation at break, and tensile strength were tested. The results indicated that the density and compressive strength increased by 128.00% and 305.64% for PUF/CT5%, respectively, compared with unfilled PUF foam. At the same time, the tensile strength and elongation at break enhanced 162.50% and 174.30% for PUF/CT4%, respectively, compared with unfilled PUF foam. Finally, the antibacterial test was carried out for PUF/CT composites using the broth dilution procedure. The results revealed that the bacterial growth was inhibited by increasing CT wt.% content. Thus, the obtained composites are promising for industrial biological applications such as packaging and medical intensive care units. Graphical abstract

Noise pollution affects human health and the environment. In this study, halloysite nanoclay (HNC) was employed as a bio-nanofiller with different ratios (1−5 wt %) to improve the thermal, mechanical, and sound absorption capabilities of the flexible polyurethane (FPU) foam. FPU/HNC composites were characterized using X-ray diffraction, Fourier transform infrared, and field emission scanning electron microscopy techniques. In addition, porosity, apparent density, and sol fraction for FPU/HNC composites were investigated. Compared with the unfilled FPU foam, the results of the FPU/HNC 1% sample showed that the density achieved a maximum value of 38.17 Kg/m 3 , while the porosity was reduced to 83.48%. Moreover, the sol fraction reached the highest value of 13.4% for the FPU/HNC 5% sample. Furthermore, thermogravimetric analysis revealed that adding 1 wt % HNC improved thermal stability than the unfilled FPU. Nevertheless, the DSC measurement proved that HNC increased the glass transition temperature (T g ) for the composites' soft segments. Intriguingly, the mechanical measurements exposed that the compressive and tensile strength of the FPU/HNC 1% sample was enhanced to 158.93 and 154.45%; at the same time, the elongation at break dropped to 124.04%. Nevertheless, the sound absorption measurements (20 mm thickness) showed a slight shift to the mid-frequency range (315−1600 Hz) for FPU/HNC composites than the unfilled FPU.

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