School of Agriculture, Food and Ecosystem Sciences - Theses

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    Increased performance and durability of boron treated wood products by acrylate and furfuryl alcohol resins
    Drvodelic, Neli ( 2000)
    Chemical modification of wood outlined in this thesis was carried out using Furfuryl alcohol and Acrylic resin. This thesis focused on impregnation of wood polymer composites (WPC) by chemical formulations that polymerise within the wood structure. A second investigation was based on the treatment of the wood with trimethyl borate (TMB) and attempts to immobilise it within the wood structure to extend the distribution of boric acid through the wood. Radiata pine (Pinus radiata D.Don) was the starting material from which WPC were made, and impregnation chemicals were TMB, furfuryl alcohol monomer, prepolymerised acrylic resin and combinations of both resins. The effect of catalysts was also investigated. Much of the work was aimed at enhancing retention of tri-methyl borate (TMB) in wood by designing the system that would lock boron based compounds within the wood. TMB was applied separately and in combination with resin formulations. The expected penetration pathway was via capillaries, pits and voids. It is postulated that after vapour diffusion of TMB into wood, TMB would hydrolyse and boric acid, the product of hydrolysis, would be deposited in the cell wall. Further, it was proposed that resin treatment would encapsulate boric acid within the cell wall during polymerisation and consequently reduce or eliminate leaching. To further improve the chances of success, momentary immersion treatment of radiata pine (Pinus radiata D.Don) with TMB in methanol and TMB in acrylic solution was also investigated. The result indicated that a greater penetration of TMB preservative would be achieved when it is applied with an acrylic solution than with methanol. From the statistical analysis, it was evident that in both cases, TMB in acrylic and TMB in methanol, TMB penetration was dependent on solution retention. In the latter case, solution retention increases with an increase in the proportion of acrylic in the solution. However, the penetration of TMB decreased as the solution viscosity increased and the penetration of TMB decreased as the concentration of methanol increased. Preservative penetration and retention were influenced by TMB concentration in both methanol and acrylic solutions. About 20% TMB was needed in an acrylic solution to penetrate about 85% of the area. In contrast, methanol solution containing 20% TMB penetrated only 60% of the area.
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    Wood characteristics and properties of plantation mountain ash (E. regnans) and their variation
    Githiomi, Joseph K ( 1992)
    Six 15-year old Eucalyptus regnans F.Muell trees from three seedlots in a progeny trial in Narbethong, Victoria were examined in this study. Wood discs were removed from the base, breast height, 20 %, 40 %, 60 % and 80 % of the total tree height. Three methods used to demarcate the boundary between the sapwood and heartwood on the disc cross sectional surface were examined. The first method was based on the difference between sapwood and heartwood. The second method which was based on the difference in pH between sapwood and heartwood used 0.1 % methyl orange stain. The third method which was based on the presence or absence of tyloses in the vessels used a light table. Measurements were also made on the cross sectional surfaces of the discs to determine the sapwood width, heartwood percent, and the number, length and year of formation of each kino vein. The presence of decay and discolouration was also noted. Sapwood and heartwood wood blocks were cut from discs along the four cardinal directions. The basic density and moisture content of all wood blocks from the four axes and the remaining pie shaped pieces from each disc were determined. Mean basic density and moisture content based on the wood blocks from only the four axes were also computed. No difference was found in the demarcation of the sapwood-heartwood boundary between the methods based on natural colour and stain. Demarcation of the boundary using the light table method gave significantly different results to those found for the colour and stain methods. Based on the light table results, the presence of the tyloses appears to vary greatly between the base and breast height while at the 20 %, 40 and 60 heights they are more uniformly distributed. The mean sapwood width varied significantly between trees with values ranging from 24.2 mm to 28.7 mm with on average about four to five growth rings present in the sapwood zone. The mean sapwood also varied significantly with height. The lowest mean sapwood width of 21.0 mm was found at breast height and the mean sapwood width increased to 33.9 mm at the 80 height and increased from breast height to 29.9 mm at the base of the tree. The mean heartwood percent varied significantly between trees and with height. Two trees from seedlot number 13 had a mean heartwood percent of about 42 which was about 6 % lower than the mean heartwood percent of about 48 for the two trees from from seedlot number 23. The largest heartwood percent of 69.51 was found at the breast height and decreased to 0 (zero) at the 80 height and also decreased from the value at breast height to 65.75 at the base of the trees. A correlation of 0.967 was found between heartwood diameter and disc diameter. Kino veins were found in all six trees with the earliest formed vein at the tree age of 4 years. For the six trees, the total number and average length of kino veins decreased with height. The average length varied greatly between trees while the total number of kino veins was relatively uniform in five out of six trees. The presence of decay and discolouration was noted in five out of six trees. Basic density varied significantly between trees and with height but not between the sapwood and heartwood which had mean basic density values of 0.430 g/cm3 and 0.435 g/cm3 respectively. The mean basic density of 0.408 g/cm3 was lowest at breast height and highest at 80 height where the mean basic density was 0.468 g/cm3. Tree number 2 from seedlot number 13 had the highest mean density of 0.486 gm/cm3 and this was significantly greater than the lowest value of 0.422 g/cm3 found for tree number 4 from seedlot number 23. The interactions between trees and heights and between heights and axes were also found to be significant. Moisture content varied significantly between trees and with height but not between the north, south, east and west cardinal directions which had mean values of 146.98 148.47 %, 148.91 and 151.15 respectively. The mean moisture content at breast height was the highest with a value of 161.14 and the lowest value of 134.33 was found at the 80 height. Tree number 2 had the lowest mean moisture content of 127.65 and tree number 5 had the highest value of 161.05%. The interactions between heights and locations (sapwood or heartwood) and between axes and locations were significant. A correlation of -0.923 was found between moisture content and basic density. The mean basic density values and the mean moisture content values determined from blocks removed along only the four axes were strongly correlated to the weighted disc values based on virtually all the wood from each disc.