Synthesis and Acoustic Study of a New Tung Oil-Based Polyurethane Composite Foam with the Addition of Miscanthus Lutarioriparius

Optimization of the Sound Absorption Coefficient (SAC) from Cellulose-Silica Aerogel Using the Box-Behnken Design

Noise pollution, which has become a major environmental issue in urban areas, can be minimized using acoustic insulation derived from cellulose-silica aerogel. The raw materials required in the process include waste newspaper-based cellulose, geothermal silica, and NaOH/ZnO solution. Therefore, this study investigates the effect of cellulose, silica, and ZnO concentrations on optimizing the sound absorption coefficient (SAC) using the Box-Behnken design (BBD). The results showed that the optimum conditions were obtained at 39.8578 wt % cellulose, 16.5428 wt % silica, and 0.5684 wt % ZnO. The impedance test for the cellulose aerogel and cellulose-silica aerogel showed SAC values of 0.59 and 0.70, respectively, and were characterized by XRD, FTIR, BET-BJH, SEM-EDX, and TG. The results of XRD and FTIR data indicate that the product was cellulose-silica aerogel, and the SEM micrographs showed that silica particles were attached to the fiber surface. Furthermore, type IV isotherms were observed in the cellulose-silica aerogel, typical of mesoporous materials. The presence of silica strengthened the aerogel structure, improved its thermal stability, and increased the surface area but decreased its pore size.

Enhancement of the mechanical and acoustical properties of flexible polyurethane foam/waste seashell composites for industrial applications

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.

Improving and Optimizing Sound Absorption Performance of Polyurethane Foam by Prepositive Microperforated Polymethyl Methacrylate Panel

Sound absorption performance of polyurethane foam could be improved by adding a prepositive microperforated polymethyl methacrylate panel to form a composite sound-absorbing structure. A theoretical sound absorption model of polyurethane foam and that of the composite structure were constructed by the transfer matrix method based on the Johnson–Champoux–Allard model and Maa’s theory. Acoustic parameter identification of the polyurethane foam and structural parameter optimization of the composite structures were obtained by the cuckoo search algorithm. The identified porosity and static flow resistivity were 0.958 and 13078 Pa·s/m2 respectively, and their accuracies were proved by the experimental validation. Sound absorption characteristics of the composite structures were verified by finite element simulation in virtual acoustic laboratory and validated through standing wave tube measurement in AWA6128A detector. Consistencies among the theoretical data, simulation data, and experimental data of sound absorption coefficients of the composite structures proved the effectiveness of the theoretical sound absorption model, cuckoo search algorithm, and finite element simulation method. Comparisons of actual average sound absorption coefficients of the optimal composite structure with those of the original polyurethane foam proved the practicability of this identification and optimization method, which was propitious to promote its practical application in noise reduction.