Effect of nanoclay content on properties of glass–waterborne epoxy laminates at low clay loading

The effect of nanoclay content on the properties of glass fibre reinforced, waterborne epoxy laminates is investigated. Fourteen ply nanocomposite laminates containing 0, 0·1, 0·2, 0·5, 1 and 2 wt-% cloisite Na⁺ nanoclay are fabricated by a hot press. The interlaminar shear strength, flexural strength and flexural stiffness of the fabricated nanocomposites are characterised. In addition, the thermal stability of the laminates is investigated using thermogravimetric analysis; the state of dispersion is studied by X-ray diffraction, and the fibre–matrix adhesion is assessed using scanning electron microscopy on fracture surfaces. Mechanical properties peaked at a nanoclay loading of 0·5 wt-%. At this low nanoclay loading, the improvements in interlaminar shear strength, flexural strength and flexural stiffness were 5, 8 and 12% respectively. Thermogravimetric analysis indicated moderate improvements in thermal stability. X-ray diffraction, on the other hand, indicated complete exfoliation of nanoclay platelets for 0·1, 0·2 and 0·5 wt-% loadings. A subtle peak appeared for nanoclay loadings of 1 and 2 wt-% at a gallery spacing of 17 Å. Scanning electron micrographs indicated improved fibre–matrix adhesion with increasing nanoclay content as evidenced by increased amount of matrix residues on the fibre bundles after fracture.