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The effects of press pressure on laboratory-made parallel strand lumbers (PSLs) that were manufactured from fast-growing rotary-peeled I-77/51 (Populus deltoides) hybrid poplar clones' veneer strands with a urea formaldehyde (UF) adhesive using press pressures ranging from 7.5 to 15 kg cm −2 in increments of 2.5 kg cm −2 were investigated. The physical and mechanical properties of PSL were affected by the press pressures. However, press pressures did not affect the combustion properties. Results indicated that higher press pressures lead to higher densification or compaction rates and specific gravities (SGs). For improved physical and mechanical properties, higher press pressures were found to be necessary. A press pressure of 12.5 kg cm −2 was found to be the optimum press pressure in relation to PSL properties. There are positive correlations among SG and mechanical properties as well as press pressures. The results may provide valuable information to assess the behavior of structural composite lumbers, including PSLs, that are manufactured using low and high press pressures. Utilization of fastgrowing tree species is possible because their strength properties are improved through pressing.

Experimental parallel strand lumbers (PSLs) were manufactured from fast growing rotary peeled I-214 (Populus x euramericana) and I-77/51(Populus deltoides) hybrid poplar clones veneer strands with melamine urea formaldehyde (MUF) adhesive. The results showed that hybrid poplar clones can be used in PSLs manufacturing. Physical and mechanical properties of PSLs were affected by clone types. The I-77/51 clone had better properties and was found to be more suitable for PSLs manufacturing compared to the I-214 clone. PSLs properties were higher than those of solid woods (SWs) and laminated veneer lumbers (LVLs) of the same poplar clones. This increase may be due to materials, densification as a result of high pressure use, and the manufacturing techniques. The degree of contribution of SWs properties to the PSLs properties was lower than that of LVLs. This indicated that factors other than SWs properties played more important roles in the strength increase of PSLs.

Experimental eight-ply laminated veneer lumbers (LVLs) from rotary peeled I-214 (Populus x Euramericana) and I-77/51 (Populus deltoides)fast growing hybrid poplar clones were successfully manufactured using three different press durations (18, 24, and 30 min) with a melamine urea formaldehyde (MUF) adhesive. The effect of press durations on LVLs’ selected physical, mechanical, and combustibility characteristics were determined. The results showed that press duration affected dimensional stability (thickness swelling and water absorption), modulus of rupture, and/or compression strength parallel to grain, depending on the clone types. Improvement in dimensional stability and some mechanical properties of LVLs can be achieved by proper curing of the MUF adhesive. On the other hand, the press durations did not affect oven-dry densities, modulus of elasticity, and the combustibility (weight loss after completion of the test). For improved physical and mechanical properties, up to a 30 min press duration can be recommended. This is necessary for LVLs when they are to be used under conditions where water and/or high humidity is present.

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