| Summary: | Most Oriented Strand Board (OSB) panels produced today contain up to 30% fines in the
core. Since substantial quantities of fines are generated during the stranding process,
there is a strong economic incentive for incorporating as much of this material into
finished panels as possible while still meeting product quality standards. The inclusion of
fines into the core of an OSB mat affects the permeability of the mat, which in turn may
affect the press cycle of the boards. There is some work on the permeability of
particleboard and OSB made from only strands or without resin in the literature, but none
on resinated mixtures of fines and strands.
For this work, OSB furnish was collected from a commercial OSB plant. The species mix
in the furnish was approximately 60% aspen, 30% pine, and 10% birch. The strands and
fines were separated by screening. A set of 45 boards was made at 3 levels of target
density and 5 different strands and fines ratios and transverse permeability of the full
thickness, surface, and core layers were measured. Vertical density profile (VDP) and
internal bond strength (IB) of the boards were also tested. The results indicate that board
density has a major effect on transverse permeability of the full thickness of the OSB
panel as well as individual layers within a board (top, bottom, and core). Fines content in
the core layer has a statistically significant effect on its permeability. In contrast, there
was no statistically significant effect of fines content on permeability of the full thickness
samples; this implies that permeability of the core layer was heavily masked by the
denser impermeable surface layers. The permeability of the core layer increases with
fines content at each panel density level with the rate of increase being higher for the high
density panels.
Based on these results, a model was developed to predict the permeability of the core of
OSB containing a mixture of strands and fines. The model considers the furnish mixture
as layers of only strands and only fines arranged in series and parallel configurations. The
inputs to the model are the mass fraction of the fines in the layer, the known permeability
of the composite comprised of 100% fines and 100% strands .layers as functions of
density, and an empirical coefficient 'α' which expresses the contribution from each model. It was found that the upper bound of the permeability data was approximately
coincident with the parallel model while the lower bound corresponded with the series
model. The permeability data were well described by a rule of mixtures combination of
the parallel and series models for α - 0.48. === Forestry, Faculty of === Graduate
|
|---|
