An Investigation into the Effect of Moisture Content on Adhesion strength of Half-polyester and Polyurethane Clear Paints Applied to Wood Surface

The present study was conducted to inverstigate the effect of moisture content on adhesion strength of sealer half-polyester and sealer polyurethane on beech (Fagus orientalis) and hornbeam (Carpinus betulus) wood types of northern regions of Iran. PH values of beech and hornbeam was 5.51 and 5.19, respectively. Dried specimens were put in a climatization room to reach moisture contents of 7%, 11% and 15%. After the preparation stage, two layers of sealer were placed on the specimens using a spray. Next, polyurethane and half-polyester were applied to the specimens. The pull-off test was performed on the specimens according to the ASTM D 4541 Standard. The results showed that the most adhesion strength was that of the sealer polyurethane used on the beech wood type with the moisture content of 7 percent and the least adhesion strength belonged to the sealer half-polyester used on the hornbeam wood type with the moisture content of 15 percent. It was also observed that increasing moisture content caused a decrease in adhesion strength of both wood types.