Evaluation of Penetration Effect of Phenol Formaldehyde Resin on Internal Bonding and Tensile Strength Parallel to Surface of Oriented Strand Board

In this study، the effect of PF resin penetration on physical and mechanical properties of OSB was evaluated. In order to make difference in resin penetration، strands were used in three different levels of 2%، 6% and 10% for MC. Mats were formed by using a special method and the boards were made with 12mm nominal thickness and 650 Kg. m3 density. Observation of bondlines was done with application of a fluorescent microscopy. Microscopic images were taken by using of a C14 Jenoptic camera equipped with a Sony progressive CCD sensor. Two parameters were defined to measure resin penetration; filled fibers number (FFN) and filled vessels number (FVN). The results showed that increase in MC has significant effect only on FFN parameter. The similar trend was found for IB but tensile strength parallel to surface and its modulus reach to their maximum amounts at 6% MC and they decreased significantly at 10% MC. The dependence of IB and tensile strength to resin penetration and thickness of adhesive was different. Thickness swelling of boards was improved with increase in MC.