The impact of wood staining on the adhesion of certain types of coating

Abstract

This paper investigates the impact of the staining of spruce wood (Picea Abies Karst.) on the adhesion of different types of coating. The samples were stained with water-based stain and lacquered using three types of transparent coatings: nitrocellulose (NC), polyurethane (PU) and waterbased coating (WB). Since the water from the stain leads to swelling of wood tissue and an increase of roughness in the surface layer, surface roughness of wood was measured before and after staining and related to the adhesion of coatings. Among unstained samples, the highest values of adhesion (4.50 MPa) was obtained in samples lacquered with WB coating, fallowing by samples lacquered with PU coating (3.72 MPa) and samples lacquered with NC coating (2.43 MPa). Staining of wood had a negative impaction the value of adhesion in the case of WB coating (4.11 MPa). The increase in surface roughness as a result of staining had a positive impaction the value of adhesion for samples which were lacquered with PU coating (4.87 MPa). The samples which were stained and lacquered with NC coating showed a slight increase in adhesion value compared to samples lacquered with same type of coating without staining (2.74 MPa).