Different reinforcement materials have been added to thermoset polymers in order to improve their physical, mechanical, chemical or thermal properties. In the last few years, graphene oxide (GO) has received attention in the scientific community due to the functional groups attached to its basal plane which provides excellent bonding conditions with polymers in order to form composites with improved properties. In this research, GO was synthesized from pristine graphite flakes through Hummers method. Graphite and GO powder morphology were examined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) was used to corroborate the oxidation process through the presence of oxygen-based functional groups, X-ray photoelectron spectroscopy (XPS) was used to determine the elemental composition of GO and its carbon to oxygen (C/O) ratio. Composites were manufactured by the addition of different GO reinforcement loadings (0.1, 0.3, 0.5, 0.8, and 1.2 wt. %) to a bio-epoxy matrix using a solution mixing method. The physical (density), mechanical (tensile and flexural), and thermal (thermal conductivity and glass transition temperature) properties were evaluated. In addition, analysis of variance (ANOVA) was performed to statistically analyze the mechanical properties and thermal conductivity of the composites. GO powder morphology was determined to be different from the morphology of graphite flakes. GO morphology was observed to have several layers with rough edges stacked on top of each other making GO to have a higher thickness in comparison to graphite. FTIR revealed the presence of different functional groups which confirmed the successful oxidation process. XPS was used to determine elemental composition of GO which was determined to be 69.58 % carbon, 29.84 % oxygen, and 0.57 % sulfur resulting in a C/O ratio of 2.3. For the bio-epoxy/GO composites, the experimental density was observed to increase with an increase in reinforcement loading. Similarly, the void content increased in the same way. The tensile and flexural properties experienced an improvement at low GO loadings of 0.1, and 0.3 wt. %. The maximum values were reached with 0.3 wt. % with an increase of 14.84, 13.20, 12.60 and 32.00 % for tensile strength, tensile modulus, flexural strength, and flexural modulus, respectively. Both tensile and flexural properties decreased when higher GO reinforcement loadings were added (0.8 and 1.2 wt. %). The thermal conductivity for GO reinforced composites was not significantly affected after the addition of GO with a maximum improvement of approximately 1 % when the reinforcement loading was 1.2 wt. %. The glass transition temperature of the composites increased as the GO loading increased with a maximum increase of 5.8 ⁰C at 1.2 wt. %. Statistical analysis revealed the tensile strength, tensile modulus, flexural strength, and flexural modulus were significantly improved with the addition of the GO reinforcement to epoxy. Therefore, epoxy/GO composites have a potential application for structural purposes due to the improvement in mechanical strength.
Master of Science (M.Sc.)