Service life prediction of chitosan-based self-healing coatings using four models and a neural network

Chitosan-based microencapsulation provides a sustainable approach for improving the durability of wood coatings; however, their resistance to coupled photo–thermal aging remains limited. In this study, three chitosan-derived microcapsule coating systems—chitosan-encapsulated wood wax oil (C–W), TiO₂- and hydroxypropyl methylcellulose (HPMC)-modified chitosan-encapsulated wood wax oil (CTH–W), and TiO₂- and HPMC-modified chitosan-encapsulated UV-curable wood wax oil (CTH–UVW)—were developed and systematically evaluated in terms of color stability, gloss retention, thermal behavior, structural degradation, and service-life prediction under accelerated photo–thermal aging. The results show that the synergistic incorporation of UV-curable wood wax oil with TiO₂-reinforced and HPMC-densified capsule walls (CTH–UVW) significantly suppresses photo-oxidation and thermal degradation. At an optimal loading of 2.0 wt%, the CTH–UVW coating exhibited markedly extended color-difference lifetime (1310.6 h) and gloss-retention lifetime (493.6 h), outperforming both C–W and CTH–W systems. Service-life modeling revealed that neural network models provided the most accurate chromaticity predictions, whereas the Weibull model yielded the most reliable gloss-retention forecasts. Complementary analyses, including mass-loss measurements, thermogravimetric displacement, SEM observations, and FTIR spectroscopy, consistently confirmed that the CTH–UVW coating maintained the highest residual mass, minimal oxidation-related spectral changes, and the least surface cracking. Notably, the 2.0 wt% CTH–UVW coating retained the strongest adhesion after aging, indicating superior interfacial stability. This work demonstrates a synergistic microcapsule design that substantially extends coating service life, offering a sustainable and high-performance solution for long-term wood protection in outdoor and architectural applications. • Three chitosan-based microcapsules enhance UV-cured wood coating durability. • 2.0% CTH–UVW microcapsule greatly extends color difference and gloss lifetimes. • Neural-network aging model excels in chromaticity prediction. • SEM/FTIR/TGA confirm strongest stability in CTH–UVW microcapsule coatings.