Viscometric, rheological, and thermodynamic studies of octafunctional epoxy resins OGDHDPBA and OGDHDPDS

In this study, we looked at the viscometric, rheological, and thermodynamic properties of two octafunctional epoxy resins: octaglycidyl dihydrazine dipropoxy para-bisphenol A (OGDHDPBA) and octaglycidyl dihydrazine 4,4′-dipropoxy diphenylsulfone (OGDHDPDS) (OGDHDPDS). The calculated degree of polymerization (DPn¯) of the synthesized OGDHDPBA and OGDHDPDS resins was in the order of 2 and 3, respectively. The viscometric characterization results revealed that the OGDHDPDS resin is more viscous than the OGDHDPBA resin. The rheological characterization results revealed that the storage (G') and loss (G'') moduli of the OGDHDPDS resin are higher than those of the OGDHDPBA resin. While thermodynamic characterization results showed that thermodynamic parameters such as glass transition temperature (Tg), activation energy (Ea), activation enthalpy variations (ΔHa), activation entropy variations (ΔSa), and activation free energy variations (ΔGa) of the studied resins (OGDHDPBA and OGDHDPDS) had the values of 105.13 and 132.86 °C; −111.49, −74.41 Kj.mol−1 (G'), −53.95 and −38.82 Kj.mol−1 (G''); –32.17, −50.29 Kj.mol−1 (G'), −42.15 and −71.16 Kj. mol−1 (G''); −257.65, −293.81 j.mol−1.K−1 (G'), −282.01, −344.94 j.mol-1.K−1 (G''); −5.08, 11.25 Kj.mol−1 (G'), −12.50 and −25.33 Kj.mol−1 (G'').