| dc.description.abstract | Excessive noise has adverse effects on human health. Therefore, it is necessary to find innovative methods for decreasing the exposure to noise in the environment. Various materials are used for dampening noise. In order to obtain promising results for sound absorption, these materials should have a large volume. Nanofibers, derived from polymeric materials, offer enormous benefits, and therefore, there is an intense focus on how this technology can be implemented to improve the performance of different applications. Nanofibers have a high surface area to volume ratio as well as a high porosity. In addition, fillers like carbon nanotubes (CNTs), wollastonite (WS), graphene (GN) and fiberglass (FG) show significant results for improving the mechanical and other properties. Therefore, in this work, polymeric nanofibers with and without fillers, have been investigated as sound absorbing materials. The polymers used in this study were polyvinyl alcohol (PVA), polyvinyl chloride (PVC), and polystyrene (PS), which were processed using electrospinning to produce nanofiber mats and tested for the sound absorption properties. To optimize fiber diameters, the process parameters were studied including the solution concentration, the solution flow rate, the high voltage used for generating an electric field, the distance over which the fibers were collected, and the speed of the rotating drum on which the fibers were collected. Statistical analysis and multiple regression techniques were applied to investigate the effects of the process parameter on the fiber diameters. Solution concentration and flow rate were determined to have the most significant effects on the fiber diameters. The study resulted in the development of a predictive model, which can be used to determine the parameter values required to produce nanofibers with a specified average diameter in the range of interest.
Various fillers were added to the polymer matrix in order to enhance its mechanical and sound absorption properties. The fillers used were CNTs, WS, GN, and FG. Single and multi-layered mats, with different fiber diameters, were produced to investigate the sound absorbing properties. Also, a mixture solution of two different polymers was electrospun to obtain a mat that consists of two polymers.
The results show that the nanofiber mats exhibit good sound absorption in the mid and low frequency ranges. As the fiber diameter decreases, the sound absorption increases. The addition of fillers to the nanofibers increases the sound absorption and improves the mechanical properties. Multi-layer mats produced from different types of polymer show a good sound absorption. The sound absorption improved using mats with graded fiber diameters structure. Increasing the mats thicknes enhances the sound absorption as well. Finally adding nanofibers mats to conventional sound absorbing materials improve the sound absorption in the low frequency range by 32%.
This study presents a promising road map for using electrospun polymer materials, with and without different types of fillers, for sound absorption in the mid and low frequency ranges. These materials will be particularly cost-effective in applications where saving space or volume is a major consideration, such as in the aerospace industry or in electronic devices. | en |
