Comparative study of some epoxy polymers based on bisphenolic and aromatic diamines: synthesis, viscosity, thermal properties computational and statistical approaches

The main objective of this study to develop an epoxy resin that is stable and does not homopolymerizes on storage. A series of di- and tetra-glycidyls of aromatic amines and alcohols were prepared. Diglycidyl of 4,4 '-dihydroxydiphenyl sulfone (DGEDDS) was prepared in a one step process by condensation with epichlorohydrin. The tetra-glycidyl of 4,4′-methylenedianiline (TGEDA) and 4,4′-(propane-2,2-diyl) diphenol, Tetraglycidyl 4-amino benzene sulfonamide (TGABSA) were obtained in satisfactory yields. The structures of the epoxy monomers were confirmed by FTIR, 1H NMR and 13C NMR spectroscopy. The viscosimetric study of the synthesized epoxy monomers showed that the bifunctional aromatic phenolic resins (DGEBA and DGEDDS) exhibited high thermostability making it possible to avoid homopolymerizing and self-crosslinking during storage. Unlike the tetra-glycidyl resins of aromatic amines (TGMDA, TGABSA and TGEDA) showed the disadvantage of self-crosslinking under the effect of temperature. The results indicate that the storage temperature for the tetra-glycidyl resins should not excess 5 °C. The bifunctional aromatic DGEDDS, should exceptional thermal stability and high fire resistance upon hardening it showed a Td of about 220 °C with a residual percentage of 40% at 500 °C. Hardened DGEBA which was used as a reference showed a Td of about 212 °C. The high thermal stability could be attributed to the presence of the sulfone group. The bifunctional aromatic amine resin TGEDA, when it is hardened with MDA it showed a Td equal of 296 °C. The increase in density of crosslinking in the case of bifunctional aromatic amine resin (TGEDA) cured with MDA enhanced the thermal resistance compared to those bifunctional aromatic phenolic resins and bifunctional aromatic amine resin (TGMDA and TGABSA). The Heteroskedasticity and autocorrelation Consistent Covariance, HAC was performed on the epoxy resins to explain the results of the thermal degradation of the examined epoxy resins as a function of the EHOMO and ELUMO, which are obtained from the optimized structure of the epoxy resins using the density functional theory. Consequently, the HAC model was validated by comparing the predicted theoretical results to experimental of thermal degradation of the studied epoxy monomers.