Epoxy/expanded graphite stacks nanocomposites for cold-cured adhesives

Abstract

Nanoscale expanded graphite stack (EGS) precursors were examined to assess their suitability to be added to a bisphenolic commercial cold-cured epoxy oligomer. The typical limits of cold-cured epoxy networks, in fact, could be surpassed with the addition of nanosized EGS. The rheological behavior of the uncured epoxy-based formulation in the presence of selected filler was first analyzed in order to evaluate the effect of addition of small amounts of the nanofiller (i.e. 3% wt.) on the processability of the liquid epoxy. The rheological measurements gave an indirect evidence of the good dispersion of nanosized EGS in the polymeric matrix, with an average aspect ratio of about 1200. The influence of the kind and the amount of graphite-ased fillers and of the production method on the morphological structure of the composites was, then, analyzed by Wide Angle X-ray diffraction and SEM analysis. A mixed intercalated and exfoliated structure were assessed and the value of the aspect ratio obtained from rheological analysis was confirmed. The influence of the presence of the nanofiller on thermal and mechanical properties of the cold-cured epoxy network was, finally, analyzed.

Keywords:

• Expanded graphite stacks
• cold-cured epoxy
• nanocomposites

Acknowledgment

The authors gratefully acknowledge Dr. Carcagnì (Mapei S.p.A., Italy) for supplying the epoxy formulation.