Design and Fabrication of Polyurethane Foams Modified with Rock Wool Fiber: The Effect of Reinforcement Amount on Acoustical and Mechanical Properties

Hypothesis: The goal of the study was to focus on improving the acoustic and mechanical properties of polyurethane foams doped with rock wool fibers, at different percentages (rock wool fiber) (0-1.2% by wt), that were synthesized using the polymerization process.

In order to fabricate acoustic composites, the relationship between non-acoustical parameters (airflow resistivity, porosity, density, and percentage of reinforcing fibers) and microstructure with sound absorption coefficient (SAC) was investigated. SAC was measured using a two-microphone impedance tube in the frequency range of 63-6400 Hz according to the ISIRI 9803 standard without an air gap behind the sample. Physical structure morphology and tensile strength were investigated using field emission scanning electron microscopy (FE-SEM) and tensile strength test, respectively. Non-acoustic measurements including porosity and air flow resistance (AFR) were performed using porosimetry test (BET) test, and Archimedes method. 

The results showed that increasing the RF amount in the polyurethane foam increased the hardness of the foam surface, and the SAC increased in all frequency range on all the studied samples. The highest SAC was shown by fiber-polyurethane composite foam (2% by wt) sample in the frequency range of 2000-4000 Hz. This increase in the sound absorption coefficient is probably related to the reduction in pore size with the increase in the amount of fibers in polyurethane foam, as shown by the morphological results. The mechanical properties (tensile strength) of foams were investigated by changing the amount of reinforcing fibers. The results showed that the tensile strength of composite foams significantly improved by adding fibers. Eventually, regression analysis was performed to investigate the relationship between non-acoustic parameters (airflow resistivity, porosity, density, and percentage of reinforcing fibers) and SAC. A relatively good fit between the experimental and statistical data was obtained. The data and results of this study showed that composite foams can be used to reduce noise.