| Résumé | Different resins used in fiber-reinforced organic-matrix composites have been characterized by means of high-performance size-exclusion chromatography (HPSEC). By using a single column packed with 5-μm particles of highly cross-linked styrene-divinylbenzene copolymer, together with tetrahydrofuran as eluent, efficient separation is achieved in less than 8 min. Of the different systems analysed, Narmco Rigidite 5208 was chosen for a more complete study involving optimization of the separation and determination of the peaks which are most suitable for characterizing the epoxy resin. HPSEC was also used to check the batch-to-batch reproducibility in this system and to evaluate the aging which occurs when it is exposed at 22°C and 50% relative humidity. The peak corresponding to the amine hardener was found to be the most appropriate for following the advancement of the curing reaction. An index obtained by dividing the total area of peaks corresponding to molecules of higher molecular weight by the area of peaks corresponding mainly to monomers was used as an indicator of the degree of polymerization. In spite of the lower resolution achieved in HPSEC compared with high-performance liquid chromatography, a rapid separation based on molecular size can be useful for controlling the quality of an epoxy system and for determining the degree of polymerization. |
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