Electrochemically Exfoliated Graphene as a Functional Additive in Ethylene-Vinyl Acetate (EVA) Composites: Mechanical Performance and Preliminary Flame-Behavior Evaluation

The incorporation of flame-retardant additives into ethylene-vinyl acetate (EVA) polymer has been shown to enhance its thermal stability and reduce flammability for various applications. This research has employed an electrochemical exfoliation method to synthesize few-layered graphene (G1) and multi-layered graphene (G2) as potential flame-retardant additives in EVA polymer, comparing their effectiveness to that of commercial carbon black (CB), a traditional flame-retardant material. Solvent-based approaches were utilized to fabricate frameworks for these composites. The flammability of the specimens was assessed following vertical and horizontal UL-94 flame test protocols, while their thermal stability was analyzed through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were utilized to examine the structural characteristics of the graphene additives. The findings from the tensile tests indicated that the percentage of elongation at break (%EB) of EVA diminished from 912% to 463.5% and 235%, respectively, with the incorporation of 10 wt.% and 15 wt.% of CB. Conversely, the introduction of 0.5 wt.% of G1 and G2 resulted in %EB values of 511 and 703, respectively, suggesting a comparatively smaller decrease in %EB. The tests revealed that for optimal efficacy, CB requires a substantial concentration (about 10-15 wt.%) while suffering from smoke emission upon combustion. G1 and G2 additives exhibited superior performance compared to CB at lower concentrations (up to 0.5 wt.%). Particularly, in the horizontal burning test, the incorporation of G1 and G2 reduced the burning rate from 31.57 mm/sec for pure EVA to 10.71 mm/sec and 13.04 mm/sec for graphene-incorporated EVA, respectively. Moreover, TGA analysis indicated that G1 prevented decomposition at T80%, with a residual char of 34.88%, the highest among the samples. DSC analysis showed that G1, with 24.48% crystallinity and the melting enthalpy of 70 J/g, is comparable to neat EVA and does not alter the nature of EVA. Ultimately, for its few-layered structure with a few oxygen functional groups, the EVA containing 0.5 wt.% G1 was identified as the suitable option. • Electrochemically synthesized 2D graphene is a more effective flame retardant than carbon black. • Graphene additives require a lower concentration with effectively inhibit smoke release. • Multi-layered graphene is more effective in a vertical burning position. • Functionalized graphene is more effective in a horizontal burning position.