Effects of phenol-formaldehyde/isocyanate hybrid adhesives on properties of oriented strand lumber (OSL) from rubberwood waste

The objective of this research project was to study the effects of hybrid adhesives of Phenol-Formaldehyde (PF) and Polymeric Diphenylmethane Diisocyanate (MDI) on the properties of Oriented Strand Lumber (OSL) to determine the optimal ratio of both adhesives. The results showed that OSL formed by pure adhesive or hybrid adhesives (3 blends: 25:75, 50:50 and 75:25) had properties that pass the CSA O437.1 standards, such as (1) modulus of rupture, (2) modulus of elasticity, and (3) internal bond strength. However, the thickness swelling and bond durability of OSL formed by pure MDI failed to pass the standards, while those formed by pure PF or hybrid adhesives passed. Among the three blends of adhesives, the blend 75:25 (PF: MDI) gave the best properties while ratio of 50:50 gave the worst properties, especially internal bond strength due to the phase separation of both adhesives. In addition, the modulus of rupture and modulus of elasticity in the "edgewise" direction were higher than those in the "flatwise" direction. In the edgewise direction, load is transferred in the direction of width of strand that is large while in the flatwise direction, load is transferred in the direction of thickness of strand which is small.