Surpassing Neat PA6: Synergistic Enhancement of Toughness and Hydrogen Barrier Properties in OMMT-Containing PA6/POE- <i>g</i> -MAH/EVOH Nanocomposite

Polyamide 6 (PA6) is a promising liner candidate for type IV hydrogen storage vessels, yet its practical application is limited by the inherent trade-off between toughness and hydrogen barrier properties. Although a previously developed PA6/POE- g -MAH/EVOH ternary blend achieves excellent impact strength and low hydrogen permeability, its overall barrier property remains slightly inferior to neat PA6. To address the limitation, organo-montmorillonite (OMMT) was introduced via a two-step melt-blending process to prepare the PA6/POE- g -MAH/EVOH/OMMT quaternary nanocomposites. Our findings demonstrate that the exfoliated OMMT drives phase morphology reorganization, reducing the density of core–shell structures while promoting a more finely dispersed EVOH phase, as evidenced by XRD and SEM. The microstructural evolution enables the optimal quaternary composite, S80E20V8M3, to achieve a 376.99% increase in impact strength (54.33 kJ/m 2 ) at 23 °C and a 542.74% increase (23.91 kJ/m 2 ) at −30 °C, alongside a 14.54% reduction in hydrogen permeability (2.41 × 10 –14 cm 3 ·cm/(cm 2 ·s·Pa)) relative to neat PA6 (2.82 × 10 –14 cm 3 ·cm/(cm 2 ·s·Pa)). Moreover, the quaternary composites further exhibit excellent thermal stability and reduced hygroscopicity. This work elucidates the OMMT-driven synergistic mechanism in the quaternary composites, thereby establishing an effective design strategy for developing high-performance PA6-based liners that integrate toughness, enhanced hydrogen barrier properties, and operational reliability for type IV hydrogen vessels.