IMPREGNATION OF FIR (Abiesborisiiregis) AND SPRUCE (Piceaexcelsa) WOOD WITH RAPE OIL AND CCB PRESERVATIVE*

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1 IMPREGNATION OF FIR (Abiesborisiiregis) AND SPRUCE (Piceaexcelsa) WOOD WITH RAPE OIL AND CCB PRESERVATIVE* Sotirios Karastergiou¹, Stergios Adamopoulos¹, Ioannis Kakaras¹, Elias Voulgaridis², Constantinos Passialis², Dafni Foti², Dimitrios Koutsianitis², Eleni Voulgaridou², Genka Blaskova³ 5 th RCCWS International Symposium.Wood structure, Properties and quality th Sep MOSCOW-Mytischi. 1 Technological Educational Institute of Thessaly, School of Technological Applications, Dept. of Wood & Furniture Design and Technology, 43100, Karditsa, Greece, s: karaso@teilar.gr, adamopoulos@teilar.gr, kakaras@teilar.gr 2 Aristotle University of Thessaloniki, School of Forestry and Natural Environment, , Thessaloniki, Greece, s: evoulga@for.auth.gr, conpas@for.auth.gr, dfoti@for.auth.gr, koutsian@for.auth.gr, v_elena7@hotmail.com ³ University of Forestry, 1756 Sofia, Bulgaria, bluskova@hotmail.com ABSTRACT The objective of this study was to examine the retention (kg/m³) and the penetration depth (mm) as well as the impregnated area of cross sections (%) along the hole length, in fir (Abiesborisiiregis) and spruce (Piceaexcelsa) wood, after preservative treatment with rape oil and CCB preservative (3.2%). The wood specimens (5x5 cm or 10x10cm in cross section and 40 cm long) with true radial and tangential surfaces,were treated with the full cell process. In order to determine the effect of direction (axial, lateral/radial or tangential) on penetration of rape oil and CCB preservative, the surfaces of the specimens were coated (laterally in all surfaces and in cross sections, respectively). Retention of rape oil ranged between and kg/m 3 in fir specimens and between and kg/m 3 in spruce specimens, while retention of CCB preservativeranged between 1.68 and kg/m 3 in fir and between 1.86 and 6.80 kg/m 3 in spruce specimens. Penetration depth in all directions as well as impregnated area of cross sections of wood specimens were found to be lower in spruce than in fir for rape oil and, in most cases, for CCB preservative tested. The general conclusion is that both species are difficult to impregnation, but fir is more permeable than spruce. Keywords: fir/spruce wood, impregnation, rape oil, CCB, retention/penetration. INTRODUCTION Wood is widely used in many exterior and semi-exterior structures with or without contact with the ground or water and is subjected to the effects of biological (fungi, insects, bacteria and marine borers) and physical (water, * This research has been co-financed by the European Union (European Social Fund ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the

2 National Strategic Reference Framework (NSRF) - Research Funding Program: Thales. Investing in knowledge society through the European Social Fund. temperature, UV light, wind) deteriorating factors (Wilkinson 1979, Voulgaridis 1980, Tsoumis 199). Hence, wood needs preventive protection with wood preservatives and other substances, especially when its uses are exterior or semiexterior, in order to prolong its service life and to maintain its value of use for longer time. The effectiveness of a preservative depends on the impregnability of wood, the type of preservative, the applied method of impregnation, the mass of preservative that is absorbed by wood (retention), the depth of penetration and deposition and distribution of preservative into the mass of wood (Richardson 1974, Kakaras and Philippou 1996). The important worldwide forest species fir and spruceprovide significant quantities of good quality solid wood but their use outdoors is limited due to low durability and refractory behavior of wood to impregnation due to its anatomical characteristics and changes like the irreversible aspiration of the flexible pit membranes in the tracheid cell walls during wood drying (Bolton and Petty 1975, Siau 1984, Usta and Hale 2006). In order to widen fir and spruce wood uses in outdoor conditions there is need to improve permeability and impregnability of wood by applying effective preparatory pretreatments(ruddick 1986,Kakaras and Voulgaridis 1992, Lehringer et al. 2009). In this work, the wood impregnability of the two refractory to impregnation forest species, fir (AbiesborisiiregisMattf.) and spruce (PiceaexcelsaLink), is comparatively investigated. This information is important in order to know the degree of resistance to impregnation of these two species and to look for effective preparatory techniques (i.e. laser drilling process) to improve their permeability and to widen their uses. MATERIALS AND METHODS From 5 logs of different fir(abiesborisiiregismattf.) and spruce (PiceaexcelsaLink) trees of Greek origin, air-dried boards with 5 cm X 5 cm and 10 cm X 10 m in cross section and 2 m long were prepared. From these boards, experimental wood samples, 40 cm long, were cut with true radial and tangential surfaces. The wood samples were placed in a conditioning room at 20 o C and 65% relative humidity and allowed to reach an equilibrium moisture content (EMC) of 12,1-12,2 %. The mean air-dry density of both species was 0.41 g/cm 3. Before impregnation, one group of the experimental samples was coated on cross-sections and a second group on all lateral surfaces in order to determine the lateral (radial/tangential) and axial penetration of preservatives, respectively. In a third group of wood samples no coating was applied on their surfaces. The specimens were impregnated with the full-cell method in a laboratory impregnation chamber by applying a vacuum of 600 mmhg for 15 minutes and pressure of 5 bars for 30 minutes. Two preservatives, an oil type (rape oil) and a water soluble (CCB of 3.2 % concentration) were used. A red pigment wasadded

3 to rape oil in orderto be observable into the mass of woodafter the impregnation process. After the completion of the impregnation process, retention, penetration depth (mm)and impregnated area measured on cross sections (%)were determined. The determination of retention was based on samples weight before and after impregnation and on their volume before impregnation. Penetration was measured in the three directions (radial, tangential, axial) and the impregnated area was determined on cross sections along the whole length of the wood samples. RESULTS AND DISCUSSION Retention, penetration depth and impregnated area of cross sections along the sample length, are given in Tables 1 and 2, for fir and spruce wood samples tested, respectively. Table 1. Impregnation characteristics (mean values of retention, penetration and impregnated area on cross sections) of fir wood samples*. Directi on of penetra tion Dimen sions in cross section (cmxc m) Retenti on Lateral 5 x (8.84) Lateral 10 x (1.73) Axial 5 x Preservative/Impregnation characteristic Rape oil CCB Penetration depth Impreg Rete Penetration depth (mm) nated ntion (mm) Tange Radial Axi area (dry Tang Radi Axial ntial al (%) salt) ential ally ly 2.97 (1.93) [54] 7.66 (3.86) 2.08 (1.82) [54] 4.43 (3.19) (4.87) [27] (4.75) [22] (27.29) 1.68 (0.34) 6.01 (0.06) 5.39 Axial 10 x From all surfaces 5 x (4.41) (18.54) 9.99 (4.53) *In parenthesis:standard deviation and in brackets: number of measurements ly 2.04 (1.85) 8.24 (5.89) 2.40 (1.50) (7.80) Impregn ated area (%) (6.59) (3.86) [22] (36.83) (19.58) [11] (17.80) [28] Tables 1 and 2 show for both species (fir, spruce) that retention, penetration depth and impregnated area measured on cross sections are influenced by the type of preservative (rape oil or CCB salts), the direction of penetration (laterally, axially or from all surfaces) and the dimensions of the specimens in cross section (5x5 cm or 10x10 cm). The highest retention was calculated in case of preservative penetration from all surfaces (lateral and cross sections) in both species (fir : 78.51kg/m 3 for rape oil and 9.99 kg/m 3 for dry CCB salt, spruce: 90.32kg/m 3 for rape oil and 6.80 kg/m 3

4 for dry CCB salt). Retention from laterally or axially only penetrated samples was lower than that from all surfaces (Tables 1, 2). Preservative penetration in all directions was higher in fir than in spruce except CCB penetration in spruce samples of5cmx 5cm in cross section. The highest penetration was observed in longitudinal direction. It ranged from 10 to Table 2. Impregnation characteristics (mean values of retention, penetration and impregnated area on cross sections) of spruce wood samples*. Directi on of penetra tion Dim ensio ns in cross secti on (cm) Retention Lateral 5 x (1.28) Lateral 10 x (2.72) Axial 5 x Preservative/Impregnation characteristic Rape oil CCB Penetration depth Impre Retention Penetration depth (mm) gnated (mm) Tange Radial Axi area (dry Tange Radi Axi ntially ly ally (%) salt) ntially ally ally 1.26 (1.66) [51] 2.32 (1.68) 2.11 (1.00) 2.24 (2.23) (3.44) (3.83) [22] 5.58 (9.19) 3.36 (1.50) 1.86 (0.05) 5.65 Axial 10 x From all surfaces 5 x (23.80) (29.62) [24] * In parenthesis: standard deviation and in brackets: number of measurements 6.80 (3.05) 4.65 (4.36) 4.23 (3.73) [42] 3.96 (6.18) 4.35 (3.17) [42] Impregnated area (%) (12.58) (3.02) [21] (25.32) (14.57) [11] (28.32) [28] 20 cm (maximum measurable) for fir and 8 to 17 cm for spruce but only in a part of wood mass along the samples length. Radial and tangential penetration depth were low in both species (fir : mm for rape oil and ,89 mm for CCB, spruce: mm for rape oil and mm for CCB). For each sample size (5X5 cm, 10X10 cm) separately and between radial and tangential penetration the differences were small either for fir or for spruce. Retention and penetration differences between the two sizes of samples, especially for spruce, may be attributed to different mean ring width and latewood percentage of the two groups of samples (Tables 1, 2). Impregnated area, measured on cross sections (%), was found to be higher in fir almost in all cases except CCB penetration in spruce samples of 5cmX 5cm in cross section. The highest impregnated area (%) was calculated in the case of preservative penetration from all surfaces (lateral and cross sections) in both species (fir : 54,35 % for rape oil and % for CCB, spruce: % for rape oil and for CCB) (Tables 1,2).

5 Penetration of preservatives tested was found to be easier in latewood than in earlywood in both species due to a much smaller number of aspirated pits in dry latewood than in dry earlywood (Figure 1). fir - rape oil 2.01 fir - CCB impregnated area: 21.43% impregnated area: 45.56% spruce - rape oil 2.35 spruce - CCB impregnated area: 17.17% impregnated area: 36.08% 2.9 Figure 1. Radial and tangential penetration (mm) in latewood and earlywood of fir and spruce wood by rape oil and CCB preservative after impregnation. CONCLUSIONS The conclusions of this work may be summarized as follows: Fir and spruce, two very important and wood productive forest species in Europe, are refractory to impregnation with protective preservatives even after application of vacuum/pressure impregnation methods. Radial and tangential penetration of rape oil and CCB preservative is very small and limited to a few mm, ranging from 1.26 mm up to a maximum of mm for both species. Between radial and tangential penetration referred to each group of samples tested separately, no substantial differences were observed.

6 Fir wood seems to be more permeable than spruce wood in most cases since radial, tangential and axial penetration was found to be higher in fir than in spruce. In both species, penetration either of rape oil or of the waterborne preservative CCB in latewood was much easier than in earlywood. Both species are difficult to be impregnated with wood preservatives and, hence, it is necessary to find and apply preparatory techniques and processes to improve permeability and impregnability of wood in order to widen their uses in outdoor conditions. LITERATURE 1. Bauch, J. et al Investigations on the treatability of spruce. HolzRoh- Werkst. 31(3): Bolton, A.J. and J.A. Petty Structural components influencing the permeability of ponded andunpondedsitca spruce. J. Microsc. 104(1): Kakaras, J.A., Voulgaridis, E.V Effect of ponding, steaming and drill perforation on preservative treatment of fir wood (Abiescephallonica L.) with CCB. HolzRoh-Werkstoff 50: Kakaras, J.A. and J.K. Philippou Treatability of several Greek wood species with the water soluble preservative CCB. HolzRohWerkst. 54: Lehringer, C. et al A review on promising approaches for liquidpermeability improvement in softwoods. Wood FiberSci. 41(4) : Richardson, B.A Wood Preservation, 2nd edn. Spon Press, London. 7. Ruddick, J.N.R A comparison of needle and North American incising techniques for improving preservative treatment of spruce and pine lumber. HolzRoh-Werkst. 44: Siau, J.F TransportProcesses in Wood. Springer Verlag, Heidelberg, Germany. 9. Tsoumis G (1991) Science and Technology of Wood: Structure, Properties, Utilization. Van Nostrand Reinhold, NY. 10. Voulgaridis,E.1980.PhysicalFactorsAffectingthePerformanceofWater RepellentsAppliedtoWood Ph.D.Thesis,U.C.N.W.,Bangor,U.K.