Effect of Impregnation with Timbercare Aqua on the Properties of Some Woods

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, 2000).

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 (δ_o) 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, M_r 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).

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.

Table 1:	Air-dry densities of wood materials (g cm-3)

Table 2:	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 2.

Fig. 2:	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).

Table 3:	Average MOE in bending according to the type of materials and impregnation period
*LSD = 224.0, **LSD = 70,85, HG = Degrees of Homogeneity

Table 4:	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.

Fig. 3:	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.

CONCLUSION

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.