Investigation of Positron Annihilation Lifetime Spectroscopy and Tensile behavior of Graphene Oxide/Epoxy Nanocomposites

Introduction and Objectives: Positron Annihilation Lifetime Spectroscopy is a sensitive method for investigating the free volume in polymers at the atomic scale, enabling the determination of pore size, shape, and concentration. It is widely used as a complementary identification tool alongside other macroscopic experimental techniques. In this study, for the first time, PALS was employed to examine the free volume in epoxy/graphene oxide nanocomposites and its correlation with the tensile behavior of the samples.Materials and Methods: In this research, Epoxy-based samples containing different weight percentages of graphene oxide (0.1, 0.3, 0.5, and 0.7 wt.%) were analyzed using PALS. A Na22 radioisotope with an activity of ~5 µCi was used as the positron source, and fast plastic scintillation detectors with a time resolution of 225 picoseconds were employed. Uniaxial tensile tests were also conducted.Results: The results showed that the lowest free pore volume (i.e. 83.87 A3) was related to the sample containing 0.3 wt.% graphene oxide, indicating a decrease of ~ 8% in the free pore volume in this sample compared to the pure epoxy one (i.e. 90.97 A3). The best tensile behavior was obtained for the sample containing 0.3 wt. % graphene oxide (i.e. 51.1 MPa), which revealed an 18 % increase in the tensile strength compared to the pure epoxy sample (i.e. 43.3 MPa).Conclusion: In general, the results of the positron annihilation lifetime spectroscopy and tensile strength measurements of the epoxy/graphene oxide nanocomposites showed that there was an inverse relationship between the free pore volume and tensile strength.