Multifunctional Corn Husk Fiber/PLA–PBAT Hybrid Composites with Carbon-Black Percolation for Structural Self-Sensing Applications

Abstract

This study developed multifunctional polymer composites based on a PLA/PBAT (Polylactic Acid/ Poly(butylene adipate-co-terephthalate)) thermoplastic matrix reinforced with 20 wt.% corn husk fiber (CHF) and functionalized with conductive carbon black (CB) for smart consumer-electronics casings. Alkali treatment modified the lignocellulosic fiber surface, improving fiber–matrix interfacial adhesion and stress transfer within the polymer composite. Thermal characterization showed that the PLA cold-crystallization temperature decreased from 112.5°C for the unfilled blend to 104.6°C for treated-fiber composites and to 102.4°C at 6 wt.% CB, while PLA crystallinity increased from 17.2% to 32.1%. The optimized TCHF-CB4 polymer composite exhibited a tensile strength of 45.9 MPa, tensile modulus of 3.58 GPa, flexural strength of 72.6 MPa, and notched impact strength of 23.8 kJ m⁻². Its 5% mass-loss temperature was 307°C, confirming adequate thermal stability for melt processing. Electrical resistivity decreased from above 10¹⁰ Ω cm for TCHF20 to 3.4 × 10⁷, 7.8 × 10³, and 4.6 × 10¹ Ω cm at 2, 4, and 6 wt.% CB, respectively, indicating conductive-network percolation near 3–4 wt.% CB. TCHF-CB4 provided the best multifunctional polymer-composite balance, with a gauge factor of 4.8 and approximately 4.3% residual drift after cyclic loading. These results demonstrate a structurally reinforced, thermally processable, electrically responsive polymer composite suitable for integrated self-sensing casing applications. The combined action of treated fibers and conductive filler established reinforcement, crystallization, stiffness, conductivity, and sensing mechanisms.