From Mechanical Compression to Chemical Bonding: Design of an ALSR Adhesive for Heterogeneous Interfacial Sealing in Type IV Hydrogen Storage Cylind

ABSTRACT

The interfacial sealing between the aluminum alloy (AA) boss and the polyamide 6 (PA6) liner at the neck of Type IV hydrogen storage cylinders is a critical bottleneck limiting their safe service life. Traditional O‐ring mechanical seals are prone to stress concentration and premature failure, primarily driven by the significant mismatch in the coefficient of thermal expansion (CTE). In this study, a siloxane adhesion promoter (VEPS) containing epoxy and terminal vinyl groups was synthesized to modify addition‐cure liquid silicone rubber (ALSR), thereby substantially enhancing its adhesion strength. The ALSR/VEPS adhesives established a robust chemical bonding layer at the AA/PA6 interface, shifting the sealing mechanism from mechanical compression to chemical bonding. The terminal vinyl groups of VEPS were integrated into the ALSR matrix via hydrosilylation, whereas the epoxy groups formed covalent bonds with the surface hydroxyl groups of the AA and the amino groups of the PA6, respectively. Furthermore, interfacial hydrogen bonding and coordination interactions provided auxiliary reinforcement. Experimental results indicated that the optimal shear strength reached 1.103 MPa, representing a 239% increase relative to pristine ALSR. Durability assessments at 85°C and −18°C for 72 h verified the robustness of ALSR/VEPS across the wide operating temperature range typical of Type IV hydrogen storage cylinders. The developed molecular‐level chemical bonding strategy effectively replaces traditional mechanical sealing methods at the cylinder neck. Consequently, these findings establish a theoretical and material foundation for optimizing the neck of Type IV hydrogen storage cylinders while demonstrating substantial potential for engineering applications.