Synthesis of new epoxy polymers and their comparative viscosimetric, rheological, and thermal characterization

During this study, four new multifunctional epoxy resins were created such as hydroxy diphenyl sulfone bis para phosphoric ester triglycidyl ether (TGEHDSEP), bisphenol A tetrabromo dipropoxy dianiline tetraglycidyl ether (TGEDADPTBBA), para-aminophenol hexaglycidyl trianiline propoxy (HGTAPPAP), and methylene dianiline para tetra-aniline octaglycidyl ether (OGTAPMDA). These resins were characterized using Fourier Transform Infrared (FTIR) spectroscopy, and their chemical structures were confirmed via ¹H NMR and ¹³C NMR spectroscopy. The resins were thermally cross-linked with methylenedianiline (MDA) as the hardener. A viscometric study was conducted using an Ubbelohd capillary viscometer to monitor the resins’ reactivity with the MDA hardener. The rheological and thermal properties of the resulting materials were analyzed using a Haaks RHM01-RD rheometer and thermogravimetric measurements. Thermodynamic parameters, including activation energy (E_a), elastic (G’), and glassy (G’’) behaviors, were also determined. The study’s findings revealed key thermal properties of this epoxy resins that the temperature of glass transition (T_g) and energy of activation (E_a) of TGEHDSEP, TGEDADPTBBA, HGTAPPAP, and OGTPMDA resins were 28.35, 28.51, 34.41, and 45.89 kJ.mol^− 1, respectively, for the E_a and 127, 130, 133, and 136 °C for the T_g. The MDA curing of the resins improved their thermal resistance. These results indicate that OGTPMDA resin has superior thermal stability and fire resistance compared to the others. Furthermore, these results demonstrated that T_d was in the order of 265.22, 220.24, 209, and 195 °C for OGTPMDA, HGTAPPAP, TGEDADPTBBA, and TGEHDSEP resins, respectively. The results obtained are excellent with regard to the observed characteristics, which presents an opportunity to apply these resins in metallic coatings and as corrosion inhibitors in future studies.