Surface properties and moisture behaviour of pine and heat-treated spruce modified with alkoxysilanes by sol-gel process

The surface morphology and moisture behaviour of pine (Pin us sylvestris) sapwood and heat-treated spruce (Picea abies) deposited with two types of silane-based sol-gel coatings were studied by atomic force microscopy (AFM) and water contact angle measurement. The chemical composition and distribution of sol-gel coatings on wood surfaces were investigated by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The AFM images revealed that the sol-gel coatings applied by spreading covered the fine structure of the wood substrates. The surface roughness analysis of the AFM topographical images indicated that the sol-gel coatings, especially the one with short aliphatic chain, had a tendency to smooth the wood surface. The XPS results confirmed that the sot-gel coatings had successfully deposited onto pine sapwood and heat-treated spruce changing their surface chemistries. ToF-SIMS images showing Si ion distribution on treated surfaces revealed that the coatings fully covered pine sapwood surfaces. The thin coating layers formed on heat-treated spruce surfaces followed the original wood surface structure. The contact angle measurements indicated that the water repellent properties of both pine and heat-treated spruce were improved to certain extent by the sot-gel coatings. (C) 2011 Elsevier B.V. All rights reserved.