Post-yield fracture behaviour of PA-6/LDPE-g-MA/nanoclay ternary nanocomposites: semiductile-to-ductile transition

Melt-mixed ternary nanocomposites of PA-6/LDPE-g-MA/organoclay, (Cloisite^TM 30B) with microscopically confirmed flocculated-intercalated morphology have been evaluated for their plane-stress fracture and failure-modes following essential work of fracture (EWF) approach. The damping properties (tan δ) revealed nanoclay-induced chain mobility restrictions causing an increase in T_g of the nanocomposites by ~5–12 °C relative to the neat PA-6 and by ~12–21 °C relative to the optimized impact modified PA-6 matrix. A reduction in area-controlled EWF (w _e : energy dissipated in the fracture plane) value was observed with 6 wt. % of nanoclay indicating a decreased resistance to crack initiation whereas a sharp-rise in the volume-controlled fracture-parameter, i.e. non-EWF (βw _p ) by ~108 % of the composite with 4wt.-% of nanoclay loading compared to optimized PA-6 blend matrix (NLC0) showed enhanced ductility and resistance to crack propagation. A semiductile-to-ductile transition (STD) was observed in the composition range of 2–4 wt. % of nanoclay loading which is also supported by a systematic transition in the nature of deformation mode as indicated from fracture surface morphology.