Optimization of Epoxy Resin: An Investigation of Eggshell as a Synergic Filler

Epoxy resin based on bisphenol A diglycidyl ether/anhydride methyl tetrahydrophthalic/2,4,6-tris(dimethylaminomethyl)phenol (DGEBA/MTHPA/DEH 35) was produced by magnetic stirring; chicken eggshell (ES) was added as cure improver. Thermal stability, cure parameters, mechanical properties, and fracture surface were investigated by thermogravimetry (TGA), differential scanning calorimetry (DSC), tensile experiments, and scanning electron microscopy (SEM). In general, the addition of ES slightly decreased the thermal stability, being T_0.05 5% lower than that of the reference sample. The cure rate increased with the heating rates, while best results were obtained upon addition of neat membrane (M) from ES. Surprisingly, the mechanical properties were significantly improved with ES as well as with M, being the Young's modulus 18% higher, the tensile strength 50% higher, and the deformation 35% higher than those of epoxy resin. SEM images showed that the synthetic compounds presented a smooth fracture surface, while the compounds with ES and M had a rougher surface with multiplane fractures, suggesting a fracture with higher energy absorption. In conclusion, epoxy/ES composites with better performance were produced, and effective tools are provided to control and attain in the future even better properties with ecological features.