Development of an acoustic absorbing material based on sunflower residue following the cleaner production techniques

The rapid growth in the agricultural production has generated several environmental impacts with a significant contribution from vegetable waste. A substantial agricultural residue comes from sunflower cultivation, especially sunflower stems, which are used in this research to develop a renewable composite with acoustic properties for insulation panels. The research followed the cleaner production practices and the proposed composite was the result of a mixture of sunflower stalk, plaster, water, and sodium benzoate as a fungal inhibitor. Composites of different particle sizes of sunflower stem were subjected to impedance tube and stress tests. Different mesh sieves with sizes of 1.18 mm, 2.36 mm, 4.75 mm and 6.30 mm were used to standardize the processed material. The acoustic performance of the samples was evaluated in an impedance tube according to the ISO, 10534-2, where frequencies in the range from 100 Hz to 6400 Hz were tested with a tube diameter of 28 mm. The samples were later tested for mechanical stress through a three-point bending test in a threefold scheme as well, following the Brazilian standard ABNT NBR 13279:2005. Statistical analysis through ANOVA and Duncan test (significance level of 5%) proved the best prototype was found to be that of smaller particle size at a sound absorption coefficient of 0.8293. The bending strength of 0.69 MPa was found for the same prototype, which is a reasonable result in comparison to other studies with composite materials. The cost of manufacturing the renewable composite was estimated at 67% lower than that observed with commercial materials. The environmental assessment was found positive as it met the requirements of cleaner production and contributed to the study of composites development from renewable materials. (C) 2020 Elsevier Ltd. All rights reserved.