Effectiveness of bark extracts and CeO2 nano particles as coating additives for the protection of heat-treated jack pine

Abstract

High temperature heat-treatment of wood for wood preservation is more beneficial compared to chemical treatment. There are several advantages of heat-treated wood compared to kiln dried wood due to the chemical modifications during high temperature heat-treatment. Heat-treated woods have improved dimensional stability, improved thermal insulating properties, and improved biological resistance. Also high temperature heat-treatment changes wood color to a dark brown color which is very important for decorative purposes. But unfortunately this color is not stable and it changes to grey or white depending on the wood species during weathering. Protection of heat-treated wood against discoloration due to weathering is the main objective of this study without changing its natural appearance. For this purpose waterborne acrylic polyurethane base was chosen for their high durability against weathering and non toxic nature. Since heat-treated wood is green product minimal use of chemicals during coating formulation was another very important factor. For this reason natural antioxidants were extracted from barks which are easily biodegradable and the source is renewable in nature. Also CeO2 nano particles were also used alone or together with lignin stabilizer to achieve a better protection against weathering on heat-treated jack pine. The protective characteristics of these coatings are compared with highly pigmented industrial coating under accelerated weathering condition. The results showed better protection of these acrylic polyurethane coatings compared to commercially available coatings used in this study. The chemical modifications during accelerated weathering of these coated heat-treated wood surface was monitored by XPS analysis and the morphological changes took place during weathering was studied by fluorescence microscope analysis