Mechanical, Thermal and Barrier Properties of Epoxy Polymer Nanocomposites Reinforced with Nanoclay, Graphene Oxide and Carbon Nanotubes

Epoxy resin nanocomposites reinforced with nanoclay (Cloisite 30B), graphene oxide (GO), and multi-walled carbon nanotubes (MWCNTs) at filler loadings of 1–5 wt% were systematically fabricated and characterised to establish structure-property relationships governing mechanical, thermal, and moisture barrier performance. Nanofillers were dispersed in the epoxy resin via probe ultrasonication (20 kHz, 400 W, 30 min with pulse intervals) and cured with triethylenetetramine (TETA) hardener at a 10:1 epoxy-to-hardener ratio. Transmission electron microscopy (TEM) confirmed intercalated/exfoliated morphology for nanoclay and well-dispersed single-layer GO sheets and MWCNT bundles at 1–3 wt%. Tensile strength, Young's modulus, and impact strength were evaluated per ASTM D638 and D256. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to assess thermal stability and glass transition temperature (Tg). Water uptake over 168 hours immersion was measured per ASTM D570. Graphene oxide at 3 wt% yielded the maximum tensile strength improvement of 34.9% (56.8 MPa vs. 42.1 MPa neat epoxy) and impact strength improvement of 41.2% (40.1 kJ/m²). Nanoclay at 3 wt% provided the greatest water uptake reduction (30.7%) and thermal stability improvement (T₅% increased from 312°C to 368°C). Agglomeration at 4–5 wt% loadings caused performance decline in all three nanofiller systems, establishing 3 wt% as the optimum loading for epoxy nanocomposites across the investigated properties.