Cost‐Effective High Hydrogen Barrier Polyethylene Nanocomposite for Type‐ <scp>IV</scp> Pressure Vessels Liner

ABSTRACT High hydrogen permeation through polymeric liner poses a significant challenge for Type‐IV hydrogen pressure vessels, which should comply with ISO 19881 (permeation rate ≤ 6 Ncc/h/L) for commercialization. This study develops a cost‐effective HDPE‐MMT nanocomposite using a simplex lattice mixture design with PE‐g‐MA compatibilizer. Comprehensive characterization confirmed that 1–2 wt% MMT‐Na + provided a uniform dispersion and a 20%–25% increase in interlayer spacing, resulting in exfoliated structures that created tortuous diffusion pathways. The optimized 1 wt% formulation achieved a hydrogen permeability of 1.53 × 10 −16 mol H 2 ·m/m 2 ·s·Pa and a permeation rate of 5.24 Ncc/h/L at 70 MPa, meeting ISO 19881 standards and reducing hydrogen transport by 73% compared with neat HDPE. Mechanical strength improved by 12.4%, and viscosity remained suitable for blow molding. A cost analysis revealed that the optimized material was 58% cheaper than PA6. The results demonstrate that nanoclay‐modified HDPE is a practical, economical candidate for Type‐IV hydrogen vessel liners.