Effects of processing parameters on mass loss and coating properties of poplar plywood during CO₂ laser modification

Abstract

Laser surface modification is a method that uses a laser beam to irradiate the workpiece surface to change its structure and chemical components, so as to change the physical and chemical properties of the material surface. In this study, the CO₂ laser was applied to modify poplar plywood. The mass loss per unit area and paint film properties (color, glossiness and adhesion) were tested and measured to evaluate the processability of laser modification for plywood. The experimental design, data analysis and model creation were accomplished by response surface methodology. Results showed that selected laser processing parameters had a significant influence on mass loss and paint film properties. The absolute values of mass loss, lightness differences and total color differences increased observably with an increase in the laser power, while decreased with an increase in the feed speed and path scanning distance. The glossiness decreased when the laser power and path distance increased but increased with the feed speed increasing. The dark and low gloss surfaces were achieved under high intensity treatment conditions. The laser modification parameters did not have obvious effects on the paint film adhesion, and the grade of paint film adhesion reached to grade 1 according to Chinese standard (GB/T 4893.4–2013). The quadratic models were selected to evaluate the quantitative relationship between laser processing parameters and response parameters, due to the high values of determination coefficient of R². The accuracy of these models was also verified by the validation experiments. The values achieved by the prediction model were in good agreement with the results of validation experiments, which indicated that the created quadratic models could give accurate prediction for the properties variations of poplar plywood during CO₂ laser modification.