Abstract
The growing demand for efficient electromagnetic (EM) shielding materials has driven extensive research into sustainable and functionalized composites for high-frequency applications. This study investigates the electromagnetic (EM) shielding properties of Polyaniline (PAni)-functionalized woven abaca fibers, reinforced with Carbon Black (CB) VXC 72, in the ultrahigh-frequency (UHF) range (500-4500 MHz), as determined using Vector Network Analyzer (VNA). The composite was developed by functionalizing abaca fabric with PAni through in situ chemical oxidative polymerization and depositing CB via a dip-and-dry method. The morphological structure and elemental composition were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), while Fourier-transform infrared (FTIR) spectroscopy was used to confirm functional group interactions. Electrical resistivity was determined using the four-point probe method, and EMI shielding effectiveness (SE) was evaluated in the ultrahigh frequency (UHF) range of 500 MHz to 4500 MHz using a Vector Network Analyzer (VNA). Experimental results indicate that PAni/CB functionalization successfully imparted shielding properties to abaca fabric. PAni/1CB/Abaca exhibited the highest shielding effectiveness with an average SE of 5.96 dB, corresponding to 74.34% attenuation of incident electromagnetic waves, and a peak attenuation of 7.45 dB at 4.5 GHz. In contrast, 2CB/Abaca and PAni/2CB/Abaca showed selective EMI shielding, with peak attenuation values of 8.27 dB at 1.67 GHz and 7.98 dB at 1.69 GHz, respectively. The electrical resistivity measurements revealed that PAni/1CB/Abaca had the lowest resistivity at 891 Ω·cm, whereas 1CB/Abaca exhibited the highest at 5238 Ω·cm. The primary shielding mechanism was absorption rather than reflection, making the composite a lightweight, corrosion-resistant alternative to traditional metal-based EMI shields. These findings demonstrate the potential of natural fiber-based conductive composites for flexible EMI shielding applications in telecommunications, healthcare, and aerospace industries.