This study is focused on the development of sound absorbing materials based on natural fiber polymer composites. The natural fibers were modified through the alkaline treatment and the natural fiber polymer composites were fabricated using hot and cold compression hydraulic press machine. The sound absorption coefficients of the composites were measured using two-microphone transfer function impedance tube method. Characterizations of the natural fiber polymer composites were analyzed using scanning electron microscope and Fourier transform infrared spectroscopy. It was found that in all measured composites, the sound absorption coefficients increased as the frequency increased. Also, as the fiber loading increased, the sound absorption coefficients of the natural fiber polymer composites were increased. It was found that the alkaline treated fiber reinforced composites increased the sound absorption coefficients due to removal of impurities and change in the structure of composites. The alkaline treatment of fibers showed better adhesion interface between fiber and polymer as compared to untreated fibers. This can be seen clearly under morphological and spectral studies of the natural fiber polymer composites.

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In this research, biodegradable composites were prepared with zein as a polymer matrix and oil palm empty fruit bunch (OPEFB) as fiber reinforcement. The fibers were treated with sodium hydroxide (NaOH). The effects of sodium hydroxide treatment on sound absorption, thermal stability, and fiber-polymer matrix interaction in composites were examined. The acoustical sound absorption coefficients of the composites were evaluated using two-microphone transfer function impedance tube method. The spectral, thermal, and morphological studies of the composites were analyzed and characterized using scanning electron microscope (SEM), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy. It was found that in all the biodegradable composites, the sound absorption coefficients increased as the frequency increased. Increases in fiber loading caused sound absorption coefficients of the composites to increase. The sodium hydroxide treatment showed a better interface adhesion on fiber and zein matrix. It was also found that this treatment increased the sound absorption coefficients. This was supported by qualitative analysis on the SEM micrographs and FTIR spectrum.

The present study investigates the dielectric constant, loss factor and dissipation factor of pineapple leaf fiber reinforced epoxy composites as in function of fiber loading, fiber surface modification and frequency. The dielectric properties of the composites were measured using HP 16451 as the dielectric test fixture and was carried out on pineapple leaf fiber reinforced epoxy composites with varying fiber loading (5wt%, 10wt%, 15wt%, and 20wt%) and fiber subjected to sodium hydroxide treatment. It was observed that the dielectric properties of these composites were influenced by fiber loading and sodium hydroxide treatment. The dielectric constant increases with increase of fiber concentration and decrease with the increase of frequency in the case of all composites. It was also observed that the increase of dielectric constant with fiber loading was more significant at low frequency. Due to a reduction in the hydrophilic nature of pineapple leaf fiber brought about by sodium hydroxide treatment the dielectric properties of the composites was less than that of the untreated ones.

The need for alternative eco-friendly and sustainable materials has forced many researchers to focus on composites made using natural fibers and biodegradable polymer matrices. In addition to that, these natural fibers are low in cost, have good mechanical properties, biodegradability, and require less production energy. Therefore, this review paper will focus on one of the natural fibers known as Luffa cylindrica (LC) by understanding all the natural fibers' benefits. A detailed overview is provided for commonly used fiber surface treatments, surface treatment techniques, and processing techniques for various LC composites from numerous other researches. Furthermore, this paper will also discuss the characteristics, mechanical properties, and water absorption properties of LC composites before and after surface treatments, where a comprehensive understanding of LC reinforced polymer composites' behavior has been reviewed.