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Permeability of a mountain-type Douglas fir stem containing included sapwood bands Koran, Zoltan

Abstract

Permeability to creosote of sapwood, included sapwood, and normal heartwood of a mountain-type Douglas fir stem was correlated with specific gravity, growth rate, percent summerwood, tracheid length, number of longitudinal resin ducts, alcohol-benzene, acetone and ether-soluble extractive contents of the corresponding zones. The effect of pressure and temperature on creosote retention was tested on creosote retention in true sapwood, included sapwood (abnormal heartwood), and normal heartwood. Test specimens were extracted in different solvents and ease of penetration tested by creosote impregnation. Among the factors investigated in the present study, specific gravity, tracheid length, growth rate, and number of longitudinal resin ducts did not have a measurable influence on creosote retention. Percent summerwood did not vary significantly at the five positions tested. Pressure had the greatest effect on creosote retention at 212°F. for heartwood, less for included sapwood and least for sapwood. The influence of temperature on creosote retention in Douglas fir heartwood was greater at 100 psi pressure than at atmospheric pressure. The effect of alcohol-benzene and acetone-soluble extractives on wood permeability was not proven statistically significant. A visual hyperbolic relationship was obtained between ether-soluble extractives and wood permeability. The higher the extractive content, the greater the retention. Pre-treatment of samples with different solvents, in order to remove some of the extractives, improved the permeability of heartwood and included sapwood significantly but caused only a slight improvement in sapwood.

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