Abstract:
Competition for the conventional supply of wood residue utilized
by the particleboard industry is increasing. Utilization of low
quality residues by the pulp and paper industry, new sawmill and
plywood recovery techniques, and the growing practice of converting
low quality residues into steam and electrical power have all cut into
the conventional wood furnish supply of the particleboard industry.
New sources of raw material need to be located if the industry is to
maintain its present production volume and product mix. It was
hypothesized that previously unused wood residues containing small
amounts of bark could supplement the conventional supply (planer
shavings, sawdust, and plywood trim) of wood materials utilized in
particleboard fabrication if board quality was maintained.
An experiment was designed to utilize laboratory fabricated
medium density homogeneous particleboard to evaluate the effects of
supplementing bark at the rates of 5, 10, and 20 percent (oven dry
weight basis) for a standard wood furnish. Three types of bark (Douglas-fir, ponderosa pine, and red alder) were individually substituted
and compared to boards fabricated with the standard wood furnish
and to each other for significant differences in selected physical properties.
Half of the boards were bonded with urea-formaldehyde, while
phenol-formaldehyde resin was utilized for the remaining boards.
Performance between the three boards was close when compared
to each other. Increasing the rate of bark substitution linearly decreased
selected strength properties, but had little effect on dimensional
stability. On the average, modulus of rupture decreased from
7% to 24%, modulus of elasticity decreased from 4% to 17%, and internal
bond decreased from 4% to 21% for the rates of 5% to 20% bark
substitution, respectively. Red alder bark substitution enhanced
internal bond properties. Performance comparisons between the two
resins were not studied.
