Toughening of brittle polyester with functionalized halloysite nanocomposites

This study presents the role of pristine halloysite nanotubes (HNT) and silane-functionalized halloysite (s-HNT) on toughening mechanisms and initiating plastic deformation in unsaturated polyester (UPE) nanocomposite. The critical stress intensity factor (K-Ic) and the critical strain energy release rate (G(Ic)) as fracture toughness indications were measured and the relationship between the morphological structures and toughening mechanisms was identified. The results indicated that the fracture toughness values exhibited a steady-state increasing trend with the incorporation of up to 5 wt % HNT or s-HNT into the UPE resin. The 3% HNT or 3% s-HNT composites were found to obtain the highest toughness values supported with uniformly dispersed particles. The SEM observations showed different energy dissipation mechanisms are; zone shielding and shear yielding with a presence of full particle debonding with the HNT addition; and river line patterns, a tail-like structure and the formation of micro-cracks mechanisms were observed with the addition of s-HNT.