High Gas Barrier Elastomer/Boehmite Composites with Mechanical Robustness and Improved Flame Retardance Enabled by Segregated Structure with Interfacial Dynamic Cross-Links

High gas barrier rubber composites are crucial for the applications requiring the combination of high resilience and gas impermeability. Layered fillers are commonly used to enhance the gas barrier performance by reducing free volume and creating tortuous gas diffusion paths. However, it remains challenging to strengthen interfacial interactions and manipulate filler distribution, which significantly affect free volume and gas diffusion paths. Herein, we present a facile strategy to build a segregated structure in modified rubber composites with dynamic interfacial cross-linking toward mechanically robust, high gas barrier elastomer composites. Concretely, boehmite (BM) nanoplatelets modified with biobased phytic acid (PA) are utilized to cross-link epoxidized natural rubber (ENR), forming dynamic β-hydroxy phosphate ester cross-links for strong interfacial interaction. This system allows a segregated structure to be readily established by hot pressing the compounds containing ENR gum, PA-modified BM, precross-linked ENR granules and zinc acetate. The volume exclusion effect of ENR granules drives the selective dispersion of BM, generating a two-phase segregated structure with the bridged interfaces across phases formed via bond exchange of dynamic cross-links. This results in excellent gas barrier performance along with distinctly improved mechanical properties. Notably, the N2 permeability of the segregated composites is reduced by 90% to 4.23 × 10–19 m3·m/(m2·s·Pa) compared to neat ENR. Additionally, improved fire safety is achieved benefiting from the combined effects of PA, BM, and the segregated structure. This work offers a promising and scalable approach for fabricating high-performance elastomer composites that combine outstanding gas barrier properties, mechanical durability and flame retardance, making them suitable for a wide range of demanding applications.