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 rea ctions of various epoxy resin formulations based on diglycidyl ether o f bisphenol A (DGEBA) resins cured with 4,4'-diaminodiphenyl sulfone ( DDS) hardener. Stoichiometric and non-stoichiometric DGEBA/DDS resin f ormulations, using neat as well as thermoplastic toughened systems con taining two phenolic hydroxyl terminated polysulfones with different m olecular weights were involved in this study. The infra-red absorption spectra of the prepared formulations were obtained on an FTi.r. spect rometer operating in the region of 11000-4000 cm-1 and were analysed a ccording to methods described in this paper. The chemical group peaks of interest in a DGEBA/DDS spectrum were identified by a comparative s tudy with individual spectra of DGEBA and DDS monomers. Where necessar y, special model compounds were used to identify unknown bands, such a s the primary amine band at 4535 cm-1. The absorption bands of interes t were integrated to quantify the areas and then converted to molar co ncentrations. This series of quantitative analysis of the major chemic al groups in several resin systems, led us to understand not only the reaction mechanism in each system but also the cure kinetics, which sh owed strong dependence on the formulation of the system. In this paper , the details of the quantitative analysis of the infra-red spectrum f or various systems and the reaction mechanisms observed in stoichiomet ric DGEBA/DDS resin formulations are described.