Experimental Investigation οf Bio-Based Polymers Reinforced with Graphene Oxide

Graphene oxide (GO) is a commonly used additive to enhance the mechanical properties of epoxy polymers. The quality of GO and the homogeneity of its dispersion into epoxy can notably improve the mechanical properties of multifunctional polymers. This work aims to clarify contradictory results of the effect of GO on the mechanical properties of bio-based polymers by synthesizing high-quality and low-cost GO. To this end, we investigated the effect of adding solvents (acetone, THF) on the mechanical behavior of polymers subjected to several types of static loading. Five different types of materials were examined: neat epoxy (reference material), enhanced epoxy without solvent, enhanced epoxy with acetone solvent, enhanced epoxy with THF solvent, and epoxy enhanced with pure graphite powder. The concentration of GO or graphite was 0.5 wt%. The findings were analyzed using Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TGA), and Raman Spectroscopy. A significant increase in the tensile strength and fracture toughness of polymers filled with GO without solvent was observed compared to the enhanced materials with solvents. SEM analysis of the fracture surfaces revealed resin penetration into the graphene sheets, indicating strong bonding between amino groups and graphene oxide in the case of the enhanced epoxy without solvent. In contrast, in the enhanced epoxies with solvents, the GO-epoxy bonding appeared to be either deteriorated or destroyed. TGA analysis revealed that both neat and GO-reinforced resins without solvent were thermally stable up to 360 °C. Raman spectra showed epoxy ring vibrations during the curing process, indicating the quantity of free epoxides in the samples.