Superior gas barrier performance of composites containing synthesized polar epoxidized isobutylene-isoprene rubber and functionalized graphene oxide

Isobutylene-isoprene rubber (IIR) is widely used in medical seals and inner tubes due to its remarkable gas barrier properties. However, the absence of polar groups and limited interfacial affinity toward inorganic fillers limit further improvement in its gas barrier performance. Herein, IIR was epoxidized using m-chloroperoxybenzoic acid to obtain epoxidized IIR (EIIR). Graphene oxide (GO) was modified using γ-aminopropyltriethoxysilane and sodium polystyrene sulfonate (PSS) to yield functionalized GO (PSS-mGO). The PSS-mGO was further incorporated into EIIR via solution blending, and the resulting PSS-mGO/EIIR compound was blended with IIR to obtain PSS-mGO/EIIR/IIR composites. The inclusion of EIIR into the IIR matrix introduced epoxy-functionalized segments into the composite, thereby enhancing intermolecular interactions and restricting segmental relaxation. Consequently, the nitrogen permeability of the EIIR/IIR composites decreased by 42.1% relative to that of the IIR composite at an EIIR/IIR mass ratio of 1:9. Further incorporation of PSS-mGO improved filler dispersion and formed a well-developed filler network. A more tortuous diffusion pathway for gas molecules was created, reducing nitrogen permeability by up to 52.2% relative to that of the IIR composite. The results demonstrate that combining EIIR and functionalized GO is an effective strategy for improving the gas barrier performance of IIR composites.