Post-yield crack toughness behavior of polyamide-6/polypropylene grafted maleic anhydride/nanoclay ternary nanocomposites

Graphical abstract: The illustrated figure demonstrates the consistent enhancement in non-essential work of fracture (βwp) which has a correspondence to the volumetric energy dissipation mode accompanied with a systematic transition in the nature of the fracture surface morphology. Highlights: ► Post-yield fracture mechanics of ternary nanocomposites are discussed. ► Tripartite-polar-interaction governs macro-structural response of the composites. ► Crack propagation resistance increased fourfold with addition of 6 wt.% of nanoclay. ► Inverse correlation between interphase thickness and non-essential work of fracture. - Abstract: The fracture properties of melt-mixed polyamide-6 (PA-6)/polypropylene grafted maleic anhydride (PP-g-MA)/nanoclay ternary nanocomposites were investigated following essential work of fracture (EWF) approach based on post-yield fracture mechanics principles. Fourier transform infrared (FTIR) spectroscopy studies revealed distinct interactions between optimized impact-modified PA-6 based blend matrix and nanoclay whereas the incorporation of nanoclay leading to enhanced lighter phase-contrast atomic force microscope (AFM) images have indicated enhanced hard-phase fractions. FTIR revealed tripartite interactions between amide functionality, maleic anhydride moiety and hydroxyl group of the three constituents of the nanocomposite. The validity of essential work of fracture (EWF) concept to these ternary nanocomposites has been demonstrated via self-similarity and Hill's analysis. The EWF (we) showed an increase by ∼35% with the incorporation of 2 wt.% of nanoclay followed by a continuous reduction up to ∼67% in 6 wt.% of nanoclay loaded composite whereas non-EWF (βwp) increased almost consistently with the maximum up to ∼264% in the entire composition range. Thus linear increase in the resistance to crack propagation is attributed to nanoclay induced enhanced micro-fibrillation accompanied with the generation of fracture surface as revealed from scanning electron microscopy studies