Effect of surfactant and electron treatment on the electrical and thermal conductivity as well as thermal and mechanical properties of ethylene vinyl acetate/expanded graphite composites

Abstract

This study presents an investigation of the electrical and thermal conductivities of composites based on an ethylene vinyl acetate (EVA) copolymer matrix and nanostructured expanded graphite (EG). To improve the EG dispersion in EVA, EG sheets were modified by treating them with the anionic surfactant sodium dodecyl sulphate (SDS) in water. The modified SDS-EG platelets, after being filtered and dried, were melt-mixed with EVA to prepare the composites. Finally, both EVA/EG and EVA/SDS-EG composites were subjected to 50 kGy electron beam (EB) irradiation. SEM images confirm that the irradiated EVA/EG samples had improved interfacial adhesion, while the irradiated EVA/SDS-EG samples showed even better interfacial adhesion. The gel contents of the irradiated samples without and with SDS treatment increased with increase in EG loading. The EVA/EG composites exhibited a sharp transition from an insulator to a conductor at an electrical percolation threshold of 8 wt %, but with SDS-EG the electrical conductivity was extremely low, showing no percolation up to 10 wt % of filler. The EB irradiation had no influence on electrical conductivity. The thermal conductivity linearly increased with EG content, and this increase was more pronounced in the case of SDS-EG, but decreased after EB irradiation. The thermal properties were little influenced by EB irradiation, while better polymer-filler interaction and better filler dispersion as a result of SDS treatment, and the EB irradiation initiated formation of a cross-linked network, had a positive effect on the tensile properties.

Recent advances in carbon-based polymer nanocomposites for electromagnetic interference shielding

“…Nevertheless, besides the possible partial rupture of the nanoparticles during processing and thus reduction of their aspect ratio, the re-aggregation of carbon-based nanoparticles is still a possibility, which has been limited by surface modifying and/or functionalizing the nanoparticles, additionally thought to enhance the interaction and compatibility with the matrix. The enhanced compatibility, while resulting in final nanocomposites with improved functionalities and enhanced electrical conductivities at lower percolation thresholds (optimization of the conductive network), has been shown by some authors to be counterproductive in some systems, as an excessive matrix-nanoparticle interaction has been proven counterproductive in maximizing the electrical conductivity and hence the EMI SE [346,348]. Interestingly, researchers have recently contemplated a strategy to enhance the electrical conductivity of carbon-based nanocomposites based on the selective dispersion of the nanoparticles in a particular polymer phase, i.e., generating more complex polymer morphologies with polymer domains with controlled nanoparticle dispersion.…”

“…Similarly, Sefadi and co-workers [348] improved the dispersion of expanded graphite nanosheets in an EVA matrix by previously surface-modifying them with sodium dodecyl sulphate (SDS) and later on subjecting the melt-blended nanocomposites to electron beam irradiation. Nanocomposites containing the SDS-modified expanded graphite showed better interfacial adhesion than their non-modified expanded graphite nanocomposites counterparts.…”

A Short Review on the Effect of Surfactants on the Mechanico-Thermal Properties of Polymer Nanocomposites

“…The thermal conductivity of EG NP/PEVA nanocomposites increased by up to 137% when the EG NPs were modified with SDS. The increase is because the modified EG NPs have a better dispersion, which formed the constant EG NP pathways [45]. The thermal conductivity of GO NS/EDTS nanocomposites increased by up to 404% when the GO NSs were modified with HTAB.…”

Thermal Conductivity of Graphite-Based Polymer Composites

“…Sefadi et al [48] studied the influence of graphite treatment with sodium dodecyl sulphate (SDS) in water on the thermal conductivity. Moreover, the authors exposed the samples to 50-KGy electron beam irradiation to improve the interaction between graphite and ethylene vinyl acetate (EVA), as host matrix.…”