On the diffusion nature of $\alpha$-relaxation in the amorphous polymer T20-60

The temperature dependences of internal friction $Q^{-1}(T)$ for the T20-60 epoxy polymer hardened at room temperature and deposited on a glass-ceramic substrate were studied. The $Q^{-1}(T)$ dependence of the polymer structure in the region of the $\alpha$-relaxation process has a maximum associated with the diffusion of vacancy-like oxygen defects of the end groups of the epoxy resin. In the $\alpha$-relaxation region, three straight sections with different slope angles are observed in the $\ln Q^{-1}(1/T)$ dependence for the T20-60 polymerized at room temperature. Based on the $\ln Q^{-1}(1/T)$ experimental dependences, the migration energy and formation energy of vacancy-like oxygen defects of epoxy groups for the polymer under study were estimated. In the pre-hardened T20-60 polymer, in the $\alpha$-relaxation region on the $\ln Q^{-1}(1/T)$ dependence for the low-temperature branch of the $Q^{-1}$ maximum, two straight sections with different slope angles are observed, associated with the migration of vacancy-like oxygen defects entering the polymer network. The migration energy and formation energy of vacancy-like oxygen defects in the main polymer network were estimated, which turned out to be $E_{m2}$ = 0.88 $\pm$ 0.08 eV and $E_{v2}$ = 0.91 $\pm$ 0.08 eV. The $\ln Q^{-1}(1/T)$ dependence for the high-temperature branch of the $Q^{-1}$ maximum has one straight section. The assessment of the activation energy on this branch showed higher values than on the low-temperature branch of the $Q^{-1}$ maximum, which indicates the diffusion nature of the $\alpha$-relaxation process of the T20-60 epoxy binder.