Preparation and characterizations of highly filled graphene-polybenzoxazine composites
In recent years, graphene has been extensively utilized in electronic applications due to its superior electrical conductivity, high thermal conductivity and excellent mechanical properties [1, 2]. This research emphasized on the development of graphene (xGnP Grade H, XG Science, USA) filled composites based on polybenzoxazine particularly at high graphene loading (0-60wt%) [3, 4]. It was found that the density of the obtained composites was linearly increased with graphene content and the values were determined to be 1.185-1.637 g/cm3 which followed the rule of mixture suggesting negligible void in the composites samples. Mechanical and thermal properties of the graphene filled polybenzoxazine composites were examined by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The curing temperature of the composites was observed to remarkably reduce from 233oC for the as-synthesized benzoxazine resin to 196oC at 60wt% of the graphene content suggesting curing acceleration with the presence of graphene. The storage modulus (E') at room temperature of the composites was considerably enhanced with the amount of the graphene i.e. from 5.9 GPa of the neat polybenzoxazine to about 25.1 GPa at 60wt% of graphene. The glass-transition temperatures (Tg) obtained from the maximum peak of loss modulus of the graphene-filled polybenzoxazine composites were observed to be in a range of 174oC to 188oC. The Tg values increased substantially with increasing graphene content implying good interfacial interaction between the graphene filler and the polybenzoxazine matrix. Other essential properties of these highly filled composites including gas permeability, electrical and thermal conductivity are also evaluated for potential use as a bipolar plates for proton exchange membrane fuel cells.
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