Abstract:
The quality and cost of wood particle composites are substantially
determined by how the adhesive that bonds the composite is
distributed on the particles. Distribution of the adhesive is controlled
by the method of application. Currently the adhesive is applied by
spraying it onto the particles. It was hypothesized that applying the
adhesive as a foam would lead to improved adhesive distribution.
An experimental system was developed for foaming a urea
formaldehyde adhesive with liquid freon-12 and for blending the foam
with wood particles. This system was compared to systems for
applying the adhesive as a spray and bulk liquid.
Strength properties of wood particle composites made with
foamed adhesive were found to be equivalent to those with adhesive
applied as a spray. Applying foamed adhesive was superior to mixing
particles with unfoamed adhesive.
Strength properties were not correlated to adhesive distribution
according to particle size. Foam and bulk liquid application produced
adhesive distributions proportional to particle surface area. The
spray application resulted in adhesive distributed disproportionately
heavy on the larger particles relative to their surface area. Other
factors, such as the number of particles not receiving adhesive and
the uniformity of adhesive coverage on a particle surface, may explain
the differences that occurred in strength properties.
