Epoxy resin suitable for structural composite based on bisphenol A diglycidyl ether (DGEBA) was mixed with anhydride methyl tetrahydrophthalic (MTHPA) as curing agent. As catalyzer two systems were investigated, the synthetic 2,4,6-tris(dimethylaminomethyl)phenol (DEH 35), and the natural based on chicken eggshell (E) and chicken eggshell membrane (M). The influence of DEH 35, E and M on the thermal stability and curing behaviors were evaluated by thermogravimetry (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). Increasing the heating rates “S” curing plots were displayed to higher temperatures, whereas under higher catalyzer content the curing started at lower temperatures. Based on FITR spectra, consuming and development of main chemical groups connected with epoxy curing were precisely followed, corroborating TG and DSC data. Proper curing rate, thermal stability and degradation rates were reached in epoxy upon EM and M addition suggesting improved cross-linked compounds. Summing up, this work presents the curing kinetics and degradation analyses of epoxy/eggshell composites, thermodynamics and kinetics parameters are reported as well as the main molecular groups involved with phase transitions, which can help to understand and control both mechanisms.