Internal density variation of hot-pressed wood panels in response to changes in flake moisture content and press closure rate

Author

David Layne McFarland

Date of Award

8-1992

Degree Type

Thesis

Degree Name

Master of Science

Major

Forestry

Major Professor

Paul M. Winistorfer

Committee Members

Robert Little, Robert McLean

Abstract

Twenty-seven, 18 x 18 x 1/2 inch, 38 lbs/ft³, non-oriented flakeboard panels were manufactured from an Aspen furnish with three levels of flake moisture content (4%, 8%, and 12%) and three press closure rates (20, 60, and 100 seconds) in a complete factorial design with three replications. Panels were scanned with a gamma-ray densitometer for density using a 3-dimensional intense sampling scheme (grid of 8 x 8 x 16). Each scanned panel possessed 1,024 observations of density which were reassembled, using an x-y-z coordinate designation, to represent 16 surface response layers (z-layers) stepping through the panel thickness.

A preliminary study was undertaken to determine an acceptable number of density observations, with an associated sampling scheme, required to detect differences in panel z-layers due to experimental treatments. A set of panels were examined to determine relative magnitudes of density variation in three spatial components. Four panels, two pressed at a 20 second closure rate and two pressed at a 100 second closure rate, were intensively scanned on a grid of 15 x 17 x 16. A total of 4,080 observations of density were produced using this sampling strategy in order to assess the normal density variation exhibited in the x, y, and z spatial panel components in response to two extreme levels of a treatment. Variation attributed to the z dimension acted out in relative independence of the x and y dimensions. The variation in density across the x-y plane for any z-layer appeared to have random patterns and the variation appeared to remain consistent through the panel thickness.

Flake moisture content influenced density in the intermediate and core z-layers. although not all z-layers inclusive. As flake moisture content increased, density also increased, except for the core z-layers. Variation in density, as indicated by standard deviation, was not consistent across all levels of flake moisture content in the interior z-layers. As flake moisture content increased, the standard deviation of density generally increased. Overall, average standard deviation of density decreased from the face z-layers to the core z-layers across all levels of flake moisture content.

The effect of press closure rate on density was limited to z-layers in the face and intermediate regions. Density increased with faster closing times in the face z-layers and then decreased in the intermediate layers relative to the same closure rate. Standard deviation of density in response to press closure rate was consistent across fifteen of the sixteen z-layers.

The interaction of main effects was significant for the core region z-layers. Highest densities, on average, resulted when intermediate flake moisture contents were teamed with slow closure rates. Standard deviation of density varied consistently across all treatment combinations.

Recommended Citation

McFarland, David Layne, "Internal density variation of hot-pressed wood panels in response to changes in flake moisture content and press closure rate. " Master's Thesis, University of Tennessee, 1992.
https://trace.tennessee.edu/utk_gradthes/7002