CNCs and CeO2 as organic–inorganic additives to enhance HPC bio-polymer wood coatings against photochemical degradation

Abstract

Wooden objects of cultural heritage are susceptible to photochemical deterioration when exposed to UV radiation in outdoor environments, which results in the reduction of their beauty and historical value. There is increasing interest in the field of wood conservation in studying bio-polymers and bio-nanocomposite materials that have better characteristics and more compatibility with the wood components and, thus, are more likely to give positive long-term conservation outcomes. This article focuses on the preparation of organic–inorganic bio-nanocomposite thin film coatings from hydroxypropyl cellulose (HPC), cellulose nanocrystals (CNCs), and cerium nanoparticles (CeO₂) applied using solution blow spraying to protect wood surfaces outdoors. The uniform coating of nanocomposites and the thin film formation of this novel bio-nanocomposite on the wood surface were characterized by SEM imaging. The FTIR spectra of the films show that not only do CNCs improve the stability of HPC against UV radiation, but adding CeO₂ nanoparticles further optimized the UV resistance of the bio-nanocomposites. ATR analysis of treated wood surfaces shows a decrease in the formation of hydroxyl groups due to photooxidation for both HPC/CNC treatments and the organic–inorganic bio-nanocomposite HPC/CNCs/CeO₂ NPs. These results were also verified by colorimetric analysis. The UV–Vis spectra of the bio-nanocomposites showed that they absorb primarily in the UV-A and UV-B regions. Furthermore, the band gap was narrowed by adding CeO₂ NPs to the HPC matrix, leading to thin films with enhanced UV resistance.