QUANTITATIVE-ANALYSIS OF THE CURE REACTION OF DGEBA DDS EPOXY-RESINS WITHOUT AND WITH THERMOPLASTIC POLYSULFONE MODIFIER USING NEAR-INFRARED SPECTROSCOPY

Near infra-red spectroscopy techniques were used to study the cure reactions of various epoxy resin formulations based on diglycidyl ether of bisphenol A (DGEBA) resins cured with 4,4'-diaminodiphenyl sulfone (DDS) hardener. Stoichiometric and non-stoichiometric DGEBA/DDS resin formulations, using neat as well as thermoplastic toughened systems containing two phenolic hydroxyl terminated polysulfones with different molecular weights were involved in this study. The infra-red absorption spectra of the prepared formulations were obtained on an FTi.r. spectrometer operating in the region of 11000-4000 cm-1 and were analysed according to methods described in this paper. The chemical group peaks of interest in a DGEBA/DDS spectrum were identified by a comparative study with individual spectra of DGEBA and DDS monomers. Where necessary, special model compounds were used to identify unknown bands, such as the primary amine band at 4535 cm-1. The absorption bands of interest were integrated to quantify the areas and then converted to molar concentrations. This series of quantitative analysis of the major chemical groups in several resin systems, led us to understand not only the reaction mechanism in each system but also the cure kinetics, which showed strong dependence on the formulation of the system. In this paper, the details of the quantitative analysis of the infra-red spectrum for various systems and the reaction mechanisms observed in stoichiometric DGEBA/DDS resin formulations are described.