Effect of lignin biopolymer, microfibre, and rubber matrix on the mechanical, fatigue, dielectric, and electromagnetic shielding properties of composites

Abstract

This research investigates the mechanical, fatigue, electromagnetic interference (EMI) shielding, and dielectric properties of rubber-based composites reinforced with a combination of flax microfibres and palm kernel shell lignin. The study evaluates the effect of incorporating these natural reinforcements on the composite’s overall performance. The results indicate that the RFL2 composite, containing 3% volume fraction of lignin biopolymer, exhibits the most superior properties. Its tensile strength increased from 19 MPa to 29 MPa, and its tear strength improved from 42 MPa to 56 MPa, suggesting enhanced load distribution and resistance to crack propagation. The hardness of the RFL2 composite also rose to 48 Shore-D, signifying increased rigidity. Furthermore, RFL2 showed significantly improved durability under cyclic loading, with a fatigue life of 12,453 cycles at 25% of ultimate tensile strength (UTS), demonstrating superior matrix-fibre interaction. In terms of electromagnetic properties, RFL2 achieved high EMI shielding effectiveness of 24.16 dB at 8 GHz and 52.36 dB at 18 GHz, indicating that lignin enhances both wave absorption and reflection. The composite also displayed optimal energy dissipation and charge storage capacity, with a dielectric permittivity of 3.66 and a dielectric loss of 0.60. Scanning electron microscopy (SEM) analysis confirmed these findings by revealing excellent interfacial bonding and uniform filler dispersion. In conclusion, the RFL2 composite stands out as a high-performance material with potential applications in electrical, structural, and protective industries due to its exceptional properties.