POS2-1195
Radiation-Induced Free Volume Evolution in Cyanate Ester Resin Characterized by Positron Annihilation Lifetime Spectroscopy
Topic
S2. High-End Characterization/Polymer Physics/Properties
When and Where
Sep 30, 2026
08:30 - 09:30
Room 301 (Grand Ballroom)
Session Chairs
Hae Jung SON
Boseok KANG
Presenter(s)
Youngsu Jeong (Korea Atomic Energy Research Institute / HANARO Utilization Division)
Co-Author(s)
Abstract
Cyanate ester (CE) is a high-performance thermosetting resin widely used in aerospace composites. In this study, positron annihilation lifetime spectroscopy (PALS) was used to investigate the dose-dependent evolution of free volume in CE resin. CE specimens were cured at 180 ℃ for 2 h. Low-dose irradiation (1–200 kGy) was performed using a 100 MeV proton beam at the Korea Multi-purpose Accelerator Complex (KOMAC), whereas high-dose irradiation (1.64–9.84 MGy) was conducted using the Pneumatic Transfer System of the HANARO research reactor at the Korea Atomic Energy Research Institute (KAERI). Positron lifetime spectra were analyzed using PALSfit3 and the Tao–Eldrup model to determine the free volume hole radius (R) and fractional free volume (FFV). The short-lifetime components (τ1 and τ2) exhibited dose-dependent variations without a systematic trend. In contrast, τ₃ increased from 1748.0 ± 8.8 ps to 1822.6 ± 10.7 ps at 100 kGy (4.3%) and then continuously decreased to 1716.5 ± 8.8 ps at 9.84 MGy. I3 remained nearly constant in the low-dose region but decreased from 22.62 ± 0.24% to 19.36 ± 0.20% in the high-dose region. R and FFV exhibited trends similar to τ₃, reaching maximum values of 2.680 ± 0.011 Å and 3.28 ± 0.08% at 100 kGy, respectively, before decreasing to 2.573 ± 0.009 Å and 2.49 ± 0.05% at 9.84 MGy. These results demonstrate that the free volume structure of CE resin evolves systematically with radiation dose. The initial increase in τ3, R, and FFV suggests local structural relaxation, whereas their subsequent decrease indicates progressive local structural rearrangement and molecular packing densification at higher doses. This study provides quantitative insight into the radiation-induced evolution of free volume in CE resin and its implications for the radiation durability of aerospace polymer matrix materials.
