Variations of Furfuryl alcohol and Wolmanit CX ... - Skog og landskap

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Variations of Furfuryl alcohol and Wolmanit CX-8 treatability of pine sapwood within and between trees ABSTRACT Erik Larnøy 1* , Stig Lande 1 & Geir I. Vestøl 2 1 Norwegian Forest and Landscape Institute Pb 115, NO-1431, Ås, Norway 2 Norwegian University of Life Sciences, Department of Ecology and Natural Resource Management *Corresponding author. Tel: +47 64949016; Email: erik.larnoy@skogoglandskap.no The variations on the ratio of filling (RoF) were investigated on Norwegian grown Scots pine (Pinus sylvestris). The samples were taken from 10 different stands in south-east Norway, and treated with furfuryl alcohol and a copper-containing wood preservative. Both within tree variations, between tree variations and variations between stands were investigated for significant differences. Factors like horizontal and vertical positioning of the stem, annual ring width, density, tree height, tree age and latitude were tested. Samples of 20 x 20 x 60 mm were impregnated with a mild treatment scheme to avoid full penetration, which made it possible to distinguish the RoF. A significant variation was found between copper impregnated a furfuryl treated samples, favouring the copper impregnated samples. Within tree variations show a positive significance of the first log compared to the other logs, and a higher RoF in younger sapwood. The latitude of the stand gave a strong correlation, favouring southern stands. Keywords: Copper, furfuryl alcohol, ratio of filling (RoF), Scots pine, treatability, uptake and latitude 1. INTRODUCTION Experience in treating Scots pine with different treatment solutions shows great differences in treatability. Some sample sets have a different level of treatment than others, although the same treatment scheme and liquid are being used. When considering treatability, Scots pine is defined in EN 350-2 as “1” for sapwood and “4” for heartwood. It is already known from literature that pine sapwood has differences in permeability. Work on gas and liquid permeability was performed by Comstock (1965, 1967, 1968 and 1970) and Comstock and Côté (1968). Siau (1984) reviewed and summarised the knowledge about transport processes in wood. They found that several wood specific factors influence the permeability and the treatability of wood. These are highly varying factors among, and also within wood species, explaining the huge variation. Although a lot of research has dealt with the permeability in wood, it is directed to liquid flow in living trees. No literature has been found where differences in treatability are being explained by factors given by variance within trees or between stands. Rapp (1993) tested the penetrability of different water based impregnation solutions in eight wood species. The tests were done separately in the radial, tangential and longitudinal directions by sealing five sides of the samples with an elastic resin based sealer, and varying both pressure and time. The most prominent conclusions were: 1) within a wood species and direction of uptake there is a high correlation between retention and depth of penetration, 2) due to the variation between wood species the 2
atio between depth of penetration and uptake varies and 3) uptake of impregnation solutions is dependent on interactions between the compounds of the impregnation solution and wood species. Larnøy (2005) describes the variability in the uptake in pine by wood preservative with four different viscosities, in the radial tangential and longitudinal direction. The main conclusion was that the lower the ability for uptake of impregnation solution, the more the viscosity influences the uptake. As wood preservatives containing metals are facing restriction in some countries both a copper containing preservative (Wolmanit CX-8) and a wood modification (furfurylation) were used in this test. Wood modification with furfuryl alcohol (FA) was discovered several decades ago. The main research focused on the catalytic systems used for the furfurylation prosess. Novel systems with FA-soluble catalysts, mainly maleic anhydride, were used, which produce stable solutions and have good impregnation properties. Today the process technology is commercialised and furfurylated wood with enhanced properties is produced (Epmeier et al. 2004, Lande et al. 2004, Westin et al. 2003, Westin et al. 2004). Due to a high chemical consumption the formulation was diluted using waterborne systems (Schneider 2001, Schneider and Westin 2002). Other commercialized modification are interlace treatment (Krause et al. 2004), heat treatment (Boonstra et al. 1998; Militz 2002; Rapp and Sailer 2000) and acetylation (Beckers and Militz 1994, Rowell 1990, Takahashi et al. 1989). Anatomical structures influencing the permeability of pine sapwood is believed to be: Size and frequency of radial and axial resin canals, size and frequency of parenchyma rays, frequency and size of half boarded pits between parenchyma rays and tracheids, frequency and ratio of aspiration of boarded pit pairs of tracheids, ratio of earlywood/latewood within an annual ring, amount and constitution of heartwood and presence and characteristics of resins in the sapwood. The presence and amount of these elements can vary between tree sites, between trees and within trees. These elements are further influenced by: (a) Growing speed regulated by nutrition, temperature, light and space, (b) Growing season length dependent on geographical location, (c) Provenance influencing genetic variance between trees. Process factors influencing the treatability of pine sapwood are believed to be: drying and seasoning of the wood, pit aspiration, resin flow and redistribution, and final moisture content. Steaming and drying might also lead to anatomical changes, such as damage to bordered pits, destruction of epithelial and ray parenchyma cells and the removal of resin (Matsumura et al. 1999). The treating schedule is regulated by vacuum, pressure, time and temperature, treating liquid, polarity, viscosity, surface properties, molecular size and impurities. As treatability varies a lot with treatment, it can be concluded that there must be a variation in the material being treated. Being able to differentiate which raw material having the best conditions for treatability, the industry would be able to select the wooden material most suitable for treatment. This would give a more homogeneous result, lower treatment time and lower energy consumption. The aims of this study are to analyse differences in treatability of Scots pine sapwood with copper containing preservative and furfuryl alcohol (FA) and to analyse the effect of wood origin. 3
Page 1: IRG/WP 08-40421 THE INTERNATIONAL R
Page 5 and 6: Table 1: Properties of the stands u
Page 7 and 8: 2.3 Statistical analyses Initially
Page 9 and 10: Predicted RoF % 60 50 40 30 20 10 5
Page 11 and 12: 7. REFERENCES Beckers, E P J, Milit

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