Paricá (Schizolobium amazonicum) and embaúba (Cecropia sp.) as new raw materials for particleboards
In this work two potential new species for forest plantation projects in Northern Brazil were evaluated for their suitability in particleboard production. The main evaluated parameters of the laboratory boards were pH value and buffer capacity of the particles, compaction ratio, thickness swelling, modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond (IB). The results showed that both species are highly suitable for particleboard production as they presented low densities (400–430 kg/m³), light color, good compressibility and no apparent adverse reactions after UF-resination.
EVALUATIOM OF PHYSICAL AND MECHANICAL PROPERTIES OF PARTICLEBOARD PRODUCED FROM WOOD OF Cupressus torulosa IN MIXTURE WITH Pinus taeda
The objective of this work was to evaluate the quality of particleboard produced with 100% of wood of Cupressus torulosa and in different mixing proportions with Pinus taeda . The experimental panels were produced with wood particles of Cupressus torulosa/Pinus taeda , in proportions of 100/0%, 80/20%, 60/40%, 40/60%, 20/80% and 0/100%, totaling six treatments. The panels were produced with nominal density of 0.75g/cm³, 8% urea-formaldehyde resin and 1% paraffin emulsion. The quality of the panels was evaluated by water absorption and swelling thickness 2 and 24 hours, static bending (MOE and MOR), perpendicular tension (internal bonding) and screw withdrawal. The comparative evaluations of the results of this research, with the Pinus taeda , others species referenced in the literature, and normative requirements of EN 312-2003 for commercial panels, indicated great potential of the wood of Cupressus torulosa for the particleboard production.
Effect of pH and buffering capacity of wood on the gelation time of urea-formaldehyde resin.
The pH and buffering capacity for water extract of the heartwood and sapwood of ten hardwoods and nine softwoods were determined. pH values ranged from 4.00 to 5.86 for hardwood and 4.02 to 5.82 for softwood. The gelation time for a urea-formaldehyde resin as affected by wood flour for each wood was determined. Analysis shows that a strong correlation between gel time of wood flour and either pH or acid buffering capacity of water extract exists.