High-performance EPDM elastomer nanocomposites reinforced by graphene nanoplatelets for sealing applications against SF_6(g) emissions

In this work, graphene nanoplatelets (GNPs) were compounded with ethylene propylene diene monomer (EPDM) to give enhanced SF_6(g) barrier properties, which is imperative topic but remains a gap in the literature. We have developed two scenarios of formulation, one with carbon black (CB) and graphene nanoplatelets (GNP), and one using GNPs to replace CB completely. The samples were prepared by industrial methods and were characterised by microstructural and thermal analysis. It was found that the addition of GNPs enhanced the 2SF_6(g) barrier of the samples significantly (90% reduction in permeability), more efficient than the barrier enhancement of the barrier to CO_2(g) (70% reduction in permeability), with the same filler loading. The full replacement of CB by the GNP, showed considerable benefit to improve (1) the processability (reduced the need of plasticiser amount from 60 to 5 phr) and (2) sealing mechanical properties of the samples, including hardness (Shore A 70-75) and compression set (12-13 % at 70 °C after 24 hours). We have also validated the sealing performance by testing the SF_6(g) permeability at elevated temperature up to 50 °C and increased gas pressure up to 10 bar, showing permeation coefficient at the same order of magnitude 10^-18 mol.m/m².s.Pa compared to the results obtained room temperature testing conditions with a gas pressure of 5.5 bar. It was indicated that the EPDM sample with only GNPs possesses higher potential than for long-term sealing applications, ideally to be developed for high-performance gaskets, O-rings and tapes, particularly for SF_6(g) barrier.