*Article* **Paint Pull-O**ff **Strength and Permeability in Nanosilver-Impregnated and Heat-Treated Beech Wood**

#### **Hamid Taghiyari 1,\*, Ayoub Esmailpour 2 and Antonios Papadopoulos 3,\***


Received: 7 October 2019; Accepted: 30 October 2019; Published: 1 November 2019

**Abstract:** The effects of impregnation with nanosilver suspension as well as heat treatment on pull-off adhesion strength and specific air permeability in beech specimens were studied here. The size range of silver nanoparticles was 30–80 nm. The cross-section of specimens was cold-sprayed with unpigmented sealer-clear, polyester, and lacquer paints. Heat treatment, as the most commonly used wood modification, was applied at three different temperatures of 145, 165, and 185 ◦C. Results showed that the highest and lowest pull-off strengths were found in the un-impregnated and unheated specimens painted with polyester (8.98 MPa) and the unpainted unheated nanosilver-impregnated specimens (3.10 MPa), respectively. Impregnation with nanosilver resulted in the rupture of perforation plates and pit openings, and eventually, permeability increased significantly. As for the pull-off adhesion strength, the increased permeability resulted in the adhesive being penetrated in to the pores in the wood substrate, and eventually, a significant decrease in the pull-off strengths occurred. No significant correlation was found between pull-off strength versus specific air permeability, although both properties depend on the porous structure. This was due to the fact that permeability depends on the continuous pore system, while pull-off strength is dependent on the surface pore system of the substrate.

**Keywords:** coating; modification; nanotechnology; un-pigmented paints; permeability; pull-off
