Determination of the effect of alkaline chemical modification using sodium hydroxide on the acoustic and thermal properties of bagasse fibers

Natural fibers have gained attention as sustainable alternatives due to their environmental advantages, sound absorption capability and thermal insulation properties. This study investigates alkaline treatment to improve the acoustic and thermal behavior of bagasse fibers for sustainable insulation applications. Chemical modification through alkaline treatment was performed using sodium hydroxide at concentrations of 1-4% and immersion times ranging from 2 to 24 h. Experimental designs were based on a factorial approach, and the data were analyzed using Design Expert software (version 11). Additionally, after conducting the experiments, analysis of variance (ANOVA) was used to develop models describing the relationships between the investigated parameters and response variables to predict optimal conditions. The results indicated that the concentration of sodium hydroxide and immersion time significantly influenced the fiber structure and its sound absorption coefficient. Specifically, a 3% concentration and 8-hour immersion time improved the sound absorption coefficient, whereas concentrations above 4% caused fiber deformation due to excessive reaction. Additionally, the peak sound absorption was observed in the frequency range of 1000 to 2000 Hz. The impact of alkaline treatment on thermal conductivity was minimal, with values ranging from 0.091 to 0.127 W/(m² K). Although the reference value for effective thermal insulators is typically considered to be 0.065 W/(m² K), and the measured values for treated bagasse were higher than this threshold, they remain too small to qualify bagasse as a strong thermal insulator. However, alkaline treatment increased the Sound Absorption Average (SAA) by 94.11% at low frequencies, 18.44% at mid frequencies, and 35.3% at high frequencies. Considering the economic and environmental advantages of these fibers and their growing application in polymer composites, this optimized process serves as an efficient method to enhance the compatibility of natural fibers with polymer matrices and improve the acoustic and mechanical properties of building composites.