Mechanical and sound absorption properties of open-cell polyurethane foams modified with rock wool fiber

Abstract

The main objective of this paper was to evaluate the mechanical and sound absorption properties of open-cell flexible polyurethane foams (PUFs) synthesized with different contents of rock wool fiber (RWF) (0, 0.5, 1, and 1.5) after treating with Alkaline surface treatments at 5% concentration of sodium hydroxide (NaOH) solution. Characterizations were carried out using the sound absorption coefficient (SAC), Brunauer-Emmett-Teller (BET), Barret-Joiner-Halenda (BJH), a field emission scanning electron microscope (FESEM), and the 506-B1 universal testing machine (for measurement mechanical properties). The SAC of PUFs with various contents of the RWF filler was determined using the transfer function method with impedance tube meter in the frequency range between 63 and 6400 Hz. The meso-macroporosity of the carrier was confirmed by BJH analysis. BET analysis illustrated an increment in the free surface area for polyurethane composite foams prepared with 1 wt% of RWF (PUF-RWF1) and 1.5 wt% of RWF (PUF-RWF1.5). The cell and pore sizes and pore distribution in the polyurethane composite foams showed significant differences after adding filler contents. The highest efficiency of sound absorption was obtained for PUF-RWF1.5 in the range between 500 and 4800 Hz, while the SAC did not improve significantly at the frequency above 4800 Hz for PUF-RWF1 and PUF-RWF1.5. Depending on the reinforcement rates of fibers, the mechanical properties of composites, such as compression strength and stress relaxation, were investigated. Stress relaxation and compression strength showed superior results with adding the RWF fillers compared to pure PUFs, and it is mainly due to the enhanced interfacial contacts and compatibility between the polyurethane matrix and RWF filler surfaces. The results and conclusion obtained in the experiment support the application of composite foams for acoustic and noise reduction.