Development and characterization of corncob-borax polyester composites for potential flame retardancy

Abstract The increasing demand for sustainable and flame-retardant materials has driven research into bio-based and inorganic reinforcements for polymer composites. This study investigates the effect of corncob and borax reinforcements on the mechanical and flame-retardant properties of polyester composites. Composites were fabricated using the hand lay-up method with treated-corncob (3, 9, 15 wt.%) and borax (12, 15, 18 wt.%). Mechanical testing revealed that the composite containing 15 wt.% corncob and 18 wt.% borax achieved optimum properties such as hardness (75.75 HS), impact strength (0.925 J/mm2), and tensile and flexural modulus (1.18 GPa and 1.63 GPa), representing significant improvements over pure polyester due to the synergistic interaction between the fillers and the polyester matrix. The composite with 9 wt.% corncob and 18 wt.% borax exhibited optimum tensile and flexural strength of 27.19 MPa and 51.77 MPa, respectively, compared to pure polyester. Flame-retardant tests showed that composites reinforced with 18 wt.% borax and 15 wt.% corncob exhibited a significantly lower burning rate of 3 mm/min, demonstrating superior flame resistance. Morphological analysis via SEM revealed uniform filler dispersion, while FTIR confirmed effective interaction between the fillers and the polyester matrix. XRD analysis indicated an increased crystallinity index of treated corncob, enhancing the composite's mechanical performance. These results highlight the composite's potential for applications requiring improved mechanical properties and flame retardancy, such as automotive and construction materials. This work underscores the novelty of combining borax and corncob as sustainable reinforcements in polyester composites.