Mechanical and Hydrogen Barrier Properties of PA6 / LLDPE ‐g‐ MAH Blends for Type

ABSTRACT

Polyamide 6 (PA6) has good hydrogen barrier properties but insufficient toughness for Type IV hydrogen storage vessel liners. Maleic anhydride grafted linear low‐density polyethylene (LLDPE‐g‐MAH), a reactive toughening agent, is melt‐blended with PA6 to prepare a series of PA6/LLDPE‐g‐MAH blends, while a PA6/maleic anhydride grafted high‐density polyethylene (HDPE‐g‐MAH) blend (S75HE25) is used for comparison. With increasing LLDPE‐g‐MAH content, strength and modulus decrease while toughness improves. This improvement is attributed to interfacial reaction between LLDPE‐g‐MAH and PA6 (FTIR) and uniform dispersion of LLDPE‐g‐MAH domains (SEM). The S75LE25 blend (25 wt% LLDPE‐g‐MAH) shows an elongation at break of 99.39%, exceeding 55.73% for PA6. Its impact strength reaches 17.03 kJ/m ² at 23°C and 12.77 kJ/m ² at −30°C, compared with 11.39 and 3.72 kJ/m ² for PA6, corresponding to increases of 49.52% and 243.28%, respectively. Its hydrogen permeability coefficient is 3.72 × 10 ⁻¹⁴  cm ³ ·cm/(cm ² ·s·Pa), above 2.82 × 10 ⁻¹⁴ of neat PA6, but far below the GB/T 42612‐2023 limit of 2.0 × 10 ⁻¹³ . In comparison, S75HE25 exhibits only 22.82% elongation at break, below that of PA6, impact strengths of 12.38 and 11.19 kJ/m ² at 23°C and −30°C (8.69% and 200.8% increases over PA6), and a hydrogen permeability coefficient of 3.37 × 10 ⁻¹⁴  cm ³ ·cm/(cm ² ·s·Pa). These results demonstrate that LLDPE‐g‐MAH achieves a better toughness‐barrier balance than HDPE‐g‐MAH for PA6, making S75LE25 a promising liner material.