Kinetic and structural interpretations of post-yield crack resistance behavior of polyamide-6/polyolefin-g-maleic anhydride blends

Abstract

Binary blends of polyamide-6 (PA-6)/polypropylene-grafted-maleic anhydride (PP-g-MA) and PA-6/low density polyethylene-grafted-maleic anhydride (LDPE-g-MA) were prepared with varied concentration (0-30 wt%) of maleic anhydride-grafted polyolefinic (PP) moiety as the impact modifier. The microstructural attributes and thermal properties of the blends were characterized by WAXD, FTIR, SEM, DSC, and TGA. The WAXD/DSC studies have revealed that the crystallinity of the blends decreased with the increase in the PP modifier whereas the onset of degradation temperature remained nearly unaffected. Comparative assessment of the crack toughness behavior of the blends has been carried out following the essential work of fracture (EWF) approach based on post-yield fracture mechanics (PYFM) concept. The kinetics of crack propagation of the blends has been discussed in the realms of structural and compositional parameters. An enhancement in the toughness (resistance to stable crack propagation) as indicated by a maximum in the non-EWF (bw p ) values have been observed at 10 and 20 wt% followed by a sharp and consistent drop in the composition regime of 10-20 and 20-30 wt% of PP-g-MA and LDPE-g-MA, respectively; conceptually implying possible ductile-to-semiductile transitions in the blend systems. The equivalence of PYFM-EPFM fracture parameters have been discussed following inequality criterion. Fractured surface morphology investigations revealed that the failure mode of the blends undergo a systematic transition from matrix-controlled homogeneous flow/deformation in the PP/polyamide phase to blend composition-dependent changes in the modes and extent of fibrillation via cavitation and shear-banding mechanisms.

Halloysite Nanotubes Filled in Asymmetric Blend of Polyamide 6, 12/poly (Ethylene‐Octene) Elastomer: Tough‐to‐Brittle Transition in Nanocomposites

“…The fracture of these pre‐notched specimens under tensile loading was conducted at a constant extension speed (5 mm/min at room temperature (30 ± 2 °C) while clamp distance was fixed at 40 mm) to obtain individual load‐displacement curves. The plane‐stress EWF approach based on the energy concept essentially postulates partitioning of the total energy dispensed in failure ( W ) into elastic ( W e ) and plastic ( W p ) components i.e., resistances to crack initiation and crack propagation ( w e and βw p ) corresponding to inner fracture process zone (IFPZ) and outer plastic deformation zone (OPDZ) as reported elsewhere . For each composition, at least eight specimens were tested with different ligament lengths to obtain data of acceptable statistical relevance.…”

“…The plane-stress EWF approach based on the energy concept essentially postulates partitioning of the total energy dispensed in failure (W) into elastic (W e ) and plastic (W p ) components i.e., resistances to crack initiation and crack propagation (w e and bw p ) corresponding to inner fracture process zone (IFPZ) and outer plastic deformation zone (OPDZ) as reported elsewhere. [21] For each composition, at least eight specimens were tested with different ligament lengths to obtain data of acceptable statistical relevance. Mathematically, the EWF method under plane stress conditions, valid for thin plates and sheets, rests upon the linear equation that accounts for the total work of fracture W (kJ/m 2 ) as the sum of elastic (W e ) and plastic (W p ) work of fractures.…”

Effect of chain extender and terpolymers on tensile and fracture properties of polyamide 6

“…Presence of CBC in PA6/Lotader blends caused toughness improvement by increasing the entanglement molecular weight (M e ) [19]. Further, on a closer analysis of EWF parameters, it was observed that w e values, which controlled by matrix material [8,39], were found to be greater than βw p values. Moreover, the gap between these two EWF parameters emerges more clearly for PA6_10L4700_1CBC blends, which gave maximum toughness value.…”