Impregnation is the most effective condition for protecting wood against destructive
effects (Miclasevics, 2004; Hazir et
al., 2003). If the wood materials are used without processing by preventive
chemicals, fungal stains, insect infestation, humidity, fire etc., damages the
wood with respect to the usage area. As a result of these damages, the wood
needs to be cared, maintained or replaced before its economic life ends (Ors
and Keskin, 2008; Arsenal, 1978 ). If the wood is
not impregnated but painted and varnished only, the prevention on the surfaces
is maximum for two years (Evans et al., 1992).
Many different chemicals are used for impregnation. Some of them can also reduce
the strength of lumber or plywood and effect related to the nature of the chemicals
and to the drying temperatures used in the treating process (Terziev
and Daniel, 2002; Winandy et al., 1988). Hemicellulose
content was significantly reduced depending on the type of chemical, the exposure
temperature and the specific hemicellulose residue examined. The degradation
of hemicelluloses plays an important role in the reduction of strength properties
(Susan et al., 1990).
Modulus of Elasticity (MOE) of treated jack pine samples treated in a two-step
process that involved first a copper chloride or a copper chloride-sodium borate
mixture and then a phenol-formaldehyde resin was not found to be statistically
different from that of the untreated wood (Daniel et al.,
2008). The specimens impregnated with a mixture of boric acid and T-C 3310
showed a decreasing effect, specially, bonding strength of 26% for beech and
21.9% for pine (Ozciftci and Uysal, 2004).
In the impregnation of pine and beech wood with UA salts and tar oil, the tar
oil increases compression strength by 10% and UA salts increase by some amount.
The tar oil increases the bending strength but the UA salts decrease (Gillwald,
1961). Salty impregnation materials increases the compression strength by
4.6-9.6%, but decreases the bending strength by 2.9-16% (Wazny,
1973). In all wood materials excluding Scotch pine, modulus of elasticity
in bending decreased as the impregnation period increased. It can be a result
of less interaction between the wood fiber and the impregnation material in
Scotch pine. As a matter of fact, it is acknowledged that pine species are more
resistant to chemical materials than are other wood types (Bozkurt
and Erdin, 1997).
In this research, Oriental spruce (Picea orientalis Lipsky), Scotch pine (Pinus sylvestris Lipsky), oak (Quercus petrea Liebl.) and Oriental beech (Fagus orientalis Lipsky) woods being used in furniture manufacturing were searched for the effects of impregnation with timbercare aqua on the Modulus of Elasticity in bending.
MATERIALS AND METHODS
Wood materials: The woods for the preparation of test samples are obtained from the timber sellers in Ankara by chance and woods with no defect that are knotless, not doty, have no reactionary part, that are normally grown and not damaged by fungus and insects were selected.
Impregnation material: Waterborne timbercare aqua used as an impregnation
material in this study was supplied by Hickson Timber Products Ltd., Istanbul.
Timbercare aqua is for using on door/window framing, wooden casings for metallic
window frames, shutters, flooring blocks. roof caging systems, surface covers,
eave-vault-balcony timbers and bearing components. Timbercare aqua is a non-flammable,
odorless, fluent, water borne, completely soluble in water, non-corrosive material
with a pH value of 4 and a density of 1.02 g cm-3. It is available
as a ready-made solution. It contains 0.5% w/w tebuconazole, 0.5% w/w propiconazole,
1% w/w 3-iodo-2-propynyl-butyl carbamate and 0.5% w/w cypermethrin. Before the
application of timbercare aqua on the wood material, all kinds of drilling,
cutting, turning and milling operations should be completed and the relative
humidity should be in equilibrium with the test environment. Timbercare aqua
should be applied by the brush, 1 L of impregnation material for 4-5 m2
of wood. Before the application of timbercare aqua on the wood material, all
kinds of drilling, cutting, turning and milling operations should be completed
and the relative humidity should be in equilibrium with the test environment.
The impregnated wood should be left for drying for at least 24 h. The wood material
can be painted, varnished or glued after it is fully dried (Hickson,
Determination of density: The density of wood material, used for the
preparation of test samples was determined according to TS 2472 (TS
2472, 1976). For determining the air-dry density, the test samples with
a dimension of 20x30x30 mm were kept under the conditions of 20±2°C
temperature and percentage 65±5 relative humidity up to reaching a stable
weight at the conditioned climatology room. The weights were measured with an
analytic scale of ±0.01 g precision and dimensions were measured with
a digital compass. The air-dry density (δ12) of samples were
calculated by using the following formula:
where, M12 is the air-dry weight and V12 is the volume
at air-dry conditions.
The samples were kept at a temperature of 103±2°C in the drying
oven up to reaching a stable weight for the determination of full-dry density.
Full-dried samples are cooled in the desiccator containing CaCl2
and then weighted at the scale having a precision of 0.01 g and the dimensions
were measured with a compass having a precision of ±0.01 mm. After the
volumes were determined by stereometric method, the density (δo)
was calculated by the following equation:
where, M0 is the full-dry weight and V0 is the volume of the wood material.
Determination of humidity: The humidity of test samples was determined
before and after the impregnation process according to TS 2471 (TS
2471, 1976). For this purpose, the samples with a dimension of 2x2x2 cm
are weighted and then oven dried at 103±2°C till they reach constant
weight. Then, samples were cooled in desiccator containing calcium chloride
(CaCl2) and weighed in an analytic balance of 0,01 g sensitivity.
The humidity of the sample (r) was calculated by the following formula:
where, Mr is the moist weight of the samples and M0 is the dry weight of samples.
Preparation of experimental samples: The rough drafts for the preparation
test and control samples were cut from the sapwood parts of massive woods and
conditioned at a temperature of 20±2°C and 65±3% relative
humidity for three months until reaching an equilibrium in humidity distribution.
The samples, with a dimension of 20x20x400 mm were cut from the drafts according
to TS EN 408 having 12% average value of humidity (TS EN 408,
1997).The densities and humidity ratios of all test samples were measured
before the impregnation process.
The test samples were impregnated according to ASTM D 1413-99 (ASTM
D 1413-99, 1976), TS 344 (TS 344, 1981) and TS 345
(TS 345, 1974). The test samples are dipped in the impregnation
pool immersing 1 cm below the upper surface for 10 min in short-term dipping,
2 h for medium-term dipping and 5 days for long-term dipping. The specifications
of the impregnation solution were determined before and after the process.
The processes were carried out at 20±2°C. Retention of impregnation
material (R) was calculated by using the following formula:
where, G = T2–T1 is the amount of impregnation
solution absorbed by the sample, T2 is the sample weight after the
impregnation, T1 is the sample weight before the impregnation, C
is the concentration (%) and V is the volume of samples.
Impregnated test samples were kept at a temperature of 20±2°C and 65±5% relative humidity until their weights became stable.
Application of experiment: The test of MOE was carried out according
to TS EN 408 by using the following test equipment (Fig. 1).
||Test equipment for modulus of elasticity in bending (mm)
The capacity of the universal testing equipment is 4.000 kP. Deformation at test samples was measured in a region five times the width of the sample by a tensionmeter. The deformations caused by incrementally increasing the forces were measured with a precision of 0.01 mm.
In the region of elastic deformation, MOE were calculated by the following formula:
where, ΔF is the difference between the arithmetic average of upper and lower limits of applied force in the elastic deformation region, Δf is the difference between the net rate of bending and the arithmetic average of the upper and lower limits of bending, L is the span, b is the width of test sample at cross section, h is the thickness at cross section.
Data analysis: By using four different kinds of wood and three different impregnation methods and control samples, a total of 160 samples (4x4x10) were prepared. Multiple Variance Analysis (MANOVA) technique was used to determine the differences between bending MOE of that samples. It was determined by the Duncan test whether the differences between the groups were meaningful or not.
RESULTS AND DISCUSSION
Density: Statistical values for the air–Bdry densities of samples
impregnated with timbercare aqua are shown in Table 1. Air-dry
densities have been found different according to the methods of impregnation.
Air-dry densities increased by the once and twice applications of impregnation.
Peculiarities of impregnation solutions: The pH value and density of
timbercare aqua, used in the impregnation process did not change as pH value
of 4 and a density of 1.02 g cm-3, due to the use of fresh solution
in each impregnation process.
||Air-dry densities of wood materials (g cm-3)
||Retention amounts of wood materials (kg m-3)
Retention quantities: The amount of retention for the different kinds
of wood and impregnation method interactions are shown in Table
||Results of Duncan tests (N mm-2) (*LSD = 224.0, **LSD = 70,85)
The amount of retention changes with the kind of wood and method of impregnation
and it was found the highest in Scotch pine and the lowest in oak. As the impregnation
repetition increases from once to twice the amount of retention increases. But
it was not continuous from two to three times applications of impregnation.
Modulus of elasticity in bending: The average values of MOE in bending according to the type of wood and impregnation period are shown in Table 3.
Modulus of elasticity in bending was found the highest in Oriental beech. This may be due to the highest density of Oriental beech. MOE in bending was found the highest in one times application of impregnation material timbercare aqua and the lowest in three times application. The repetition of impregnation causes a decrease in MOE. So impregnation method and repetition were found effective on the MOE. The results of multiple variance analysis of wood material and impregnation method in bending modulus of elasticity are shown in Table 4.
As a result of the Duncan test for the effects of variance sources on the bending
MOE, the difference between the groups (α = 0.05) was meaningful as shown
in Fig. 2.
According to Duncan test results, for non-impregnated woods MOE were found
the highest in Oriental beech (12,490 N mm-2), the lowest in Oriental
spruce (8,165 N mm-2) and for impregnated woods, the highest in Oriental
beech once impregnated (14,360 N mm-2) and the lowest in Scotch pine
thrice impregnated (7,246 N mm-2).
||Average MOE in bending according to the type of materials and impregnation
|*LSD = 224.0, **LSD = 70,85, HG = Degrees of Homogeneity
||Results of multiple variance analyses of wood material and impregnation
period in bending modulus of elasticity
|Int.-A : Wood materials, Int.-B: Impregnation methods
MOE according to wood materials and impregnation periods are shown in Fig.
3. At the similar studies, MOE were less in spruce than Scotch pine and
oak (Ors et al., 2006). But after the impregnation
by the timbercare aqua this value was measured as higher.
||Modulus of elasticity (N mm-2) according to wood species
and repetition of impregnation
MOE in bending decreases as the impregnation period increases in wood material
except Scotch pine. This may be due to the interaction between the wood fiber
and impregnation material. It is known that pine woods are chemically more resistant
than other woods.
In the impregnation with timbercare aqua, type of wood, impregnation method and combination of both were found effective on the bending modulus of elasticity (α = 0.05).
The highest MOE as mean values was measured in Oriental beech (13,303 N mm-2). This result is similar with the literature and may be due to the highest density of Oriental beech. In the literature, mean values of MOE were less in spruce than Scotch pine and oak but it was measured as higher by the effect of timbercare aqua.
For the combination of impregnation material and wood type, MOE was measured highest in single impregnated Oriental beech and lowest in triple impregnated Scotch pine. Needle type of woods are more resistant to chemical substances than leave woods. In this study, timbercare aqua effected Scotch pine and Oriental beech similarly but oak and Oriental spruce differently.
MOE of impregnated samples except oak were measured higher than control samples. MOE was measured highest in single impregnation (11,076 N mm-2) and decreased by the double and triple impregnation. According to this result, it can be said that timbercare aqua increases MOE of all wood except oak. A decrease in the MOE of oak wood in single impregnation and in other woods by the double and triple impregnation may be due to a decrease on the bond between the wood leafs by the oxidation effect of timbercare aqua.
As a result, the effect of timbercare aqua on MOE for the tested woods is found important. MOE of oak is decreased by impregnation with timbercare aqua but increased in the other woods. So, single impregnation of Oriental beech, Scotch pine and Oriental spruce is sufficient but for oak, using place is important for decision making in impregnation.