Sustainable bean pod/calcined kaolin reinforced epoxy hybrid composites with enhanced mechanical, water sorption and corrosion resistance properties

Abstract

The industrial and academic world is becoming more interested in advanced composite materials owing to the increasing global awareness on environmental and social issues. From this point of view, novel epoxy hybrid composites were prepared by utilizing bean pod as an agricultural waste and calcined kaolin with the addition of varying ratios (0.5–5.0 wt%) to fixed weight of 3 wt% bean pod. The resulting hybrid composites were characterized by different analyses and tests to evaluate physico-mechanical and thermal properties. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses showed uniform dispersion of hybrid filler in the neat epoxy resin which revealed better compatibility between hybrid filler and epoxy resin. Tensile strength of hybrid composite including 2 wt% calcined kaolin (39.8 MPa) was higher than those of the other hybrid composites. The water sorption percentage of the hybrid composites was effectively decreased until 0.87% with increasing amount of calcined kaolin. The hybrid composite including 5 wt% calcined kaolin exhibited highly corrosion resistance to alkali and salty solutions compared to acidic reagents. Thermogravimetric analyses (TGA) and vicat softening temperature (VST) tests revealed that an important improvement was not observed in degradation temperatures of the hybrid composites; however, residue at 650 °C increased up to 21.0% in the presence of calcined kaolin. It can be said that the hybrid composites mentioned above came into prominence with high tensile strength, quite low water uptake and excellent corrosion resistance in alkali and salty environments.