Abstract
The rheological behaviors of four aromatic amine-based epoxy monomers for were evaluated and compared. The four epoxy monomers are useful for making cross-linked epoxy resin, the monomers are triglycidyl-2 aminophenol (TGAP), triglycidyl-2-aminothiophenol (TGATP), tetra-functional tetraglycidyl-1,2-phenylenediamine (TGPDA), and tetraglycidyl-4-methyl-1,2-phenylenediamine (TGMPDA). The monomers were cured with 4, 4'-methylene dianiline (MDA). The rheological behaviors of the cured products were also evaluated. The cured epoxy monomers were characterized by FT-IR and the curing process was monitored using a Haake Mars rheometer equipped with a cone-plate geometry. During the curing process, the change in the viscosity was monitored as a function of time at various temperatures. The temperatures ranged from 120 degrees C to 150 degrees C. The curing process was temperature dependent; at 150 and 120 degrees C, a sharp rise in the viscosity was observed. The viscosity of TGPDA-MDA and TGMPDA-MDA (tetra-functional) showed a higher increase in the viscosity compared to other matrices an indication of faster formation of the 3D network. The storage moduli G' and the loss moduli and G" conditions of the macromolecular matrix structures of TGMPDA-MDA was higher than that of the macromolecular matrix structures of TGAP-MDA, TGATP-MDA and TGPDA-MDA. Quantum chemical calculations were performed using the density functional theory (DFT) to investigate the influence of electronic and molecular structure of the investigated compounds before and after cross-linking with MDA unit(s) of the examined epoxy resins. Graphic abstract