The Impact of an Ultrasound-Assisted Mixing Method for Varnish Systems on The Varnish Layer's Surface Hardness and Surface Scratch Resistance.

The objective of this study was to determine the effects of mechanical and ultrasound-assisted stirring methods for varnish systems on the varnish layer's surface hardness and surface scratch resistance. The study focused on polyurethane, acrylic, and polyester varnish systems, which were applied to three distinct wood types: Scots pine (Pinus sylvestris L.), Turkish beech (Fagus orientalis Lipsky), and African mahogany (Khaya ivorensis A. Chev.). The mixing processes included mechanical stirring for 3 and 5 minutes, as well as ultrasound-assisted stirring with differing power levels (80 W and 120 W) for 3 and 5 minutes. The highest surface hardness (175.10) was achieved using polyester varnish obtained by mechanical stirring for 3 minutes and applied to Turkish beech, while the lowest surface hardness (66.80) was observed for acrylic varnish obtained by 120 W ultrasound-assisted stirring for 5 minutes and applied to African mahogany. The highest surface scratch resistance (0.760 N) was observed with polyester varnish obtained by mechanical stirring for 5 minutes and applied to Scots pine, and also with acrylic varnish obtained by 80 W ultrasound-assisted stirring for 3 minutes and applied to Turkish beech. Overall, the findings suggested that the ultrasound-assisted mixing method generally fell short in terms of enhancing the varnish properties compared with the mechanical mixing technique. [ABSTRACT FROM AUTHOR]