Graphene/TiO2-Reinforced Bio-Based Polyamide 11 Hybrid Composites for Lightweight Engineering Applications

The development of sustainable polymer hybrid composites combining high mechanical strength, thermal stability, and improved fire response is essential for lightweight engineering applications. The primary objective of this study was to develop bio-based polyamide 11 (PA11) hybrid composites reinforced with graphene nanoplatelets (Gr) and titanium dioxide (TiO2) particles to enhance their mechanical, thermal, and fire-response properties. Scanning electron microscopy (SEM) revealed graphene nanoplatelets and TiO2-rich particulate domains distributed within the PA11 matrix, highlighting the hybrid composite morphology and its potential contribution to improved mechanical reinforcement and thermal stability. Hybrid reinforcement enhanced crystallization and thermal stability, increasing crystallization temperature from 158.5 to 163.2 °C and crystallinity from 20.4 to 25.6%. The thermal degradation temperatures (T5%, T10%, and Tmax) increased from 384.5, 398.5, and 434 °C to 411.0, 425.0, and 459 °C, respectively. The highest hybrid loading improved Young’s modulus, yield strength, and tensile strength by approximately 40%, 48%, and 30%, respectively, while DMA demonstrated enhanced thermomechanical stability. Furthermore, peak heat release rate (pHRR) decreased from 610 to 365 W g−1, corresponding to a 40.2% reduction, while the temperature at peak heat release (TpHRR) increased from 438 to 460 °C. These findings highlight the potential of Gr/TiO2-modified bio-based PA11 hybrid composites for sustainable, lightweight engineering applications requiring enhanced mechanical integrity, thermal stability, and fire resistance.