Experimental Investigation on Thermo-Mechanical, Visco-Elastic, and Acoustic Properties of Hibiscus rosa-sinensis Plant Fiber-Reinforced Polymer Composites

fibers (HRFs) for composite applications involved a multi-step process, primarily fiber extraction through water retting and subsequent surface modification by using sodium hydroxide (NaOH) and trimethoxy methyl silane (TMMS). Through the compression molding technique, untreated HRF-reinforced poly-lactic acid (PLA) composites (UHRFCs), NaOH-treated HRF-reinforced PLA composites (NHRFCs), and TMMS-treated HRF-reinforced PLA composites (THRFCs) were fabricated. The experiments were conducted, and the findings revealed a substantial increase in properties of both NHRFCs and THRFCs compared to UHRFCs. Notably, these enhancements encompassed tensile strength (13.66% and 19.39%), tensile modulus (13.41% and 20.70%), flexural strength (15.98% and 23.17%), flexural modulus (17.13% and 26.58%), impact strength (15.62% and 33.07%), Shore-D hardness (4.19% and 5.00%), storage modulus (9.88% and 13.07%), loss modulus (7.52% and 17.36%), dielectric constant at 6.5 Hz (13.22% and 23.96%), and significant improvements in the acoustic resonance frequency at 1897 Hz (79.50% and 81%). Peak thermal degradation temperatures of these composites are 420.62 ± 3.43 °C, 439.51 ± 3.54 °C, and 469.07 ± 3.11 °C, respectively, and biodegradability results showing accelerated degradation within 30 days. These findings highlight the substantial effectiveness of treatments in enhancing diverse properties, underscoring the potential applicability of these composites in various industrial sectors requiring superior performance and sustainable materials.