Closed-loop design of nuclear-grade epoxy coatings: linking bio-based curing chemistry to microstructure and performance
摘要
The long-term safety of nuclear power plants requires organic coatings that retain adhesion and structural continuity under combined thermal, radiolytic, and chemical loading associated with design-basis accident (DBA) scenarios. In this work, a closed-loop formulation–microstructure–performance strategy was implemented to develop an epoxy coating for nuclear applications, with emphasis on a biomass-derived phenalkamine curing agent (107). Cure behavior of three epoxy/amine systems (2029-4, 2259, 107) was quantified by FTIR peak integration of the oxirane band at 910–917 cm−1 together with DSC and DMA. The epoxy-107 system exhibited the deepest cure and the highest network density, achieving a glass transition temperature of 85.5 °C and a crosslink density of approximately 1.4 × 10−3 mol/cm3 at an optimal epoxy:amine equivalent ratio of 1:0.82, surpassing the conventional aliphatic and cycloaliphatic amines. High-throughput screening of defoamers, dispersants, leveling agents, and filler combinations, followed by SEM and X-ray microcomputed tomography, yielded an additive package that reduced coating porosity to about 0.15% and ensured uniform pigment/filler dispersion. Under simulated DBA conditions and 0.1 M HNO3 immersion, the optimized epoxy-107 coating maintained film integrity with only slight surface wrinkling, lower water uptake, and higher adhesion retention than the 2259-cured counterpart. The superior durability is attributed to the hybrid molecular architecture of phenalkamine 107, in which aromatic segments provide thermal rigidity while long aliphatic chains confer hydrophobicity and stress relaxation. The results demonstrate that bio-based phenalkamines can deliver nuclear-grade performance and provide a transferable framework for designing sustainable epoxy coatings for extreme service environments.