Application of acrylic-based varnishes reinforced with nano fillers for conservation of weathered and worn surfaces of the historical and cultural wooden buildings

Abstract

The aim of this study was to investigate the surface protection effects of acrylic-based varnishes including TiO2 and Al2O3 nano-fillers in the conservation process of naturally aged and worn surfaces of historical and cultural wooden structures. The varnishes were applied to the wood surfaces with a brush and the varnish-coated samples were artificially aged in a weathering cabin. The changes in the surfaces of the samples were evaluated according to color change, micro hardness, abrasion tests, scratch tests, surface durability, and surface characterization via scanning electron microscopy (SEM). The thermal properties and morphological characterization of the varnishes with nano-fillers were also determined, and ultraviolet-visible (UV-vis) and FTIR analyses were performed. The results showed that the micro hardness, abrasion, and scratch values of the varnishes were not statistically significant. However, the values of the varnishes with TiO2 were determined to be slightly higher than those of the varnishes with Al2O3. The surface durability of the neat varnish was significantly improved by adding the nano-fillers. With the addition of the nano-fillers, the SEM revealed reduced thickness of the varnishes on the surfaces of the wood samples. The thermal properties, optical properties with UV-vis, and morphological structure of the neat varnish were improved by adding the nano-fillers, whereas the FTIR detected no difference in the bonding of the varnishes. The UV spectra of TiO2 and Al2O3 generally showed a peak at 354nm and 210nm wavelengths, which means that they exhibited good absorbance in the UV region. The results indicated that adding nano-fillers to the neat varnish could generally improve the outdoor performance and lifetime of historical and cultural wooden structures.