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Abstract
Recently, graphene-polymer composites gained a central role in advanced stress and strain sensing. A fundamental step in the production of epoxy-composites filled with graphene nanoplatelets (GNPs) consists in the exfoliation and dispersion of expanded graphite in a proper solvent, in the mixing of the resulting GNP suspension with the polymer matrix, and in the final removal of the solvent from the composite before curing through evaporation. The effects of traces of residual solvent on polymer curing process are usually overlooked, even if it has been found that even a small amount of residual solvent can affect the mechanical properties of the final composite. In this paper, we show that residual traces of N,N′-Dimethylformamide (DMF) in vinylester epoxy composites can induce relevant variations of the electrical, mechanical and electromechanical properties of the cured GNP-composite. To this purpose, a complete analysis of the morphological and structural characteristics of the composite samples produced using different solvent mixtures (combining acetone and DMF) is performed. Moreover, electrical, mechanical and electromechanical properties of the produced composites are assessed. In particular, the effect on the piezoresistive response of the use of DMF in the solvent mixture is analyzed using an experimental strain dependent percolation law to fit the measured electromechanical data. It is shown that the composites realized using a higher amount of DMF are characterized by a higher electrical conductivity and by a strong reduction of Young’s Modulus.
Highlights
Over the last decade, graphene-polymer composites have attracted growing attention for both civil and military applications [1,2]
graphene nanoplatelets (GNPs) based polymer composites have been widely investigated in various engineering applications, including electromagnetic compatibility [9,10,11,12,13], protection from electrostatic discharge (ESD) [14,15], structural sensing and monitoring [16,17,18,19,20,21]
Scope of this paper is to investigate the electrical, mechanical and electromechanical properties of graphene-polymer composites prepared through exfoliation of expanded graphite in a solvent mixture containing acetone and DMF
Summary
Graphene-polymer composites have attracted growing attention for both civil and military applications [1,2]. The development of metal-free conductive fillers has driven the interest for electrically conductive polymer composites which can combine good electrical properties with the typical characteristics of polymeric materials, such as lightweight, high formability and resistance against corrosion [2,3]. Polymers 2018, 10, 82 well as to poor processability. Within this context, nanofillers have attracted growing attention from the scientific community. GNP based polymer composites have been widely investigated in various engineering applications, including electromagnetic compatibility [9,10,11,12,13], protection from electrostatic discharge (ESD) [14,15], structural sensing and monitoring [16,17,18,19,20,21]
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