The shear strength of Calabrian pine (Pinus brutia Ten.) bonded with polyurethane and polyvinyl acetate adhesives

Abstract

ABSTRACT:In this study, the change in shear strength on radial and tangential surfaces of Calabrian Pine (Pinus brutia Ten.) wood having different roughness values as the result of sawing with a circular ripsaw, planing and sanding, and bonded with polyurethane (PU) and polyvinyl acetate (PVAc) adhesives at the pressure levels of 3, 6, and 9 kgf/ cm 2 , was studied. Each of the 360 specimens prepared to determine the effect of the variables on bond performance were subjected to shear test in an universal test machine in accordance with the ASTM D 905-98 standards. The values obtained were analyzed statistically and the results were interpreted. The highest shear strength (11.83 N/mm 2 ) for plane of cut was obtained on the tangential surface after sanding and applying PVAc adhesive with a pressing pressure of 9 kgf/cm 2 . The lowest shear strength (6.01 N/mm 2 ) was obtained in the joinings made on the planed surfaces by using PU adhesive and a pressing pressure of 3 kgf/cm 2 .The highest shear strength (9.10 N/mm 2 ) on the radial surface was obtained after sanding and applying PVAc adhesive and pressing with a pressure of 6 kgf/cm 2 . The lowest shear strength (3.76 N/mm 2 ) was obtained in the specimens whose surfaces were sanded and glued with PU adhesive with a pressing pressure of 3 kgf/cm 2 . In general, in the radial surfaces, just like in the tangential surfaces, the specimens bonded with PVAc exhibited a higher shear strength compared with those glued with PU. According to these results, it is definitely necessary to sand the surfaces prior to the bonding process to have a higher shear strength. The bonding process should be made on the tangential surfaces with higher pressures. The PVAc adhesive should be preferred instead of the PU adhesive.

Determination of the Effect of Surface Roughness on the Bonding Strength of Wooden Materials

“…Results were found in the literature that shows that surface roughness affects bonding strength. This study showed results similar to the literature (Burdurlu et al 2006;Yang et al 2012;Knorz et al 2015;Kılıç 2016).…”

“…The first group displayed the highest bonding strength (7.38 N/mm 2 ) from the aspect of surface roughness; this was followed by the second group (6.57 N/mm 2 ), and finally the third group (5.89 N/mm 2 ). Similar results were determined in the study of Burdurlu et al 2006. The PVAc adhesive produces higher shear strength values compared with the PU adhesive.…”

“…It was reported in previous studies that the wooden material whose density was high also had a high bonding strength (Söğütlü et al 2016;Burdurlu et al 2006;Kılıç 2016).…”

“…Particularly in such cases, the noted wood failure percentage (WFP) of one and the same sample can vary quite a bit, depending on the person evaluating it (Künniger 2008;Kläusler et al 2014;Hass et al 2014). According to Burdurlu et al (2006), the shear strength values of black pine specimens bonded with PVAc adhesive were higher (8.16 N/mm 2 ) than those bonded with PUR adhesive (7.95 N/mm 2 ). Experimental results and statistical analysis suggest that processing pressure is the most important factor, and penetration is a secondarily important factor in determining adhesion strength.…”

Determination of the Surface Roughness Values of Turkish Red Pine (Pinus brutia (Ten.)) Woods

“…The roughness values of the tangentially cut surfaces were determined to be lower than the radially cut surfaces. Burdurlu et al (2006) have also determined that the Ra values of tangentially cut samples of red pine trees were lower than the values of radially cut surfaces. In the same manner, the Ra values of surfaces processed with the thickness machine were found to be lower compared to surfaces sanded with no: 80 sandpaper ( Table 5).…”