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Impacts of some chemicals on combustion properties of impregnated laminated veneer lumber (LVL)
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
journal homepage: www.elsevier.com/locate/jmatprotec
Review
Impacts of some chemicals on combustion properties of impregnated laminated veneer lumber (LVL) ¨ ¸ ifc¸i a,∗ , Oktay Okc¸u b Ayhan Ozc a b
¨ University, Technical Education Faculty, 78050 Karabuk, ¨ Turkey Karabuk Cumhuriyet University, Akdagmadeni College, 66300 Yozgat, Turkey
a r t i c l e
i n f o
a b s t r a c t
Article history:
The objective of this study was to investigate the effects of zinc chloride (ZnCl2 ) and borax
Received 27 May 2007
(Na2 B4 O7 ·5H2 O) on combustion properties of laminated veneer lumbers (LVLs) with two,
Received in revised form
three and four-layered, produced from white oak (Quercus alba) and chestnut (Cestanea sativa
27 September 2007
Mill.) woods. Veneers obtained for LVL were impregnated according to ASTM-D 1413. Veneers
Accepted 8 October 2007
applied vacuum method were dried and bonded with poly(vinyl) acetate (PVAc) and D-VTKA polyurethane-based adhesives. The combustion test was performed according to the procedure defined in the ASTM-E 69 standard. The results indicated that the highest weight
Keywords:
loss of LVL (43.1 g) was observed in unprocessed weigh wood samples. The lowest O2 con-
LVL
sumption ratio was in borax-impregnated LVL samples with Desmodur-VTKA, with a ratio
Impregnation
20.4%. The highest CO ratio observed in LVL control samples was 2834.7 ppm, the highest
Combustion
temperature measured in borax-impregnated control LVL was 398.5 ◦ C, the highest ash ratio
Zinc chloride
was measured as 82.4%, however NOx and SOx emissions (oxides of nitrogen and sulfur) could not be measured, because heat did not go up to 1000 ◦ C. As a result, borax was found
Borax
to be an effective fire-retardant chemical in LVL. In conclusion, it can be recommended as a fire-retardant building material. © 2007 Elsevier B.V. All rights reserved.
Contents 1. 2.
∗
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Impregnation chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Adhesives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Impregnation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Preparation of test samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5. Humidity and air-dry density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6. Execution of the combustion test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7. Statistical procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Corresponding author. Tel.: +90 370 433 82 00; fax: +90 370 433 82 04. ¨ ¸ ifc¸i). E-mail address: [email protected] (A. Ozc 0924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.10.003
2 2 2 2 3 3 3 3 4
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j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
3. 4. 5.
1.
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction
Laminated wood materials are named differently according to the layer thicknesses used. A material having a thickness of 25.4–50.8 mm used in producing large dimensioned laminated solid wood material which is used in building sector and it is named as glued-laminated lumber (GLULAM). The veneer with a thickness of 3.2 mm is used in producing small-sized laminated solid materials and those kind of laminated materials are named as laminated veneer lumber (LVL) or MICROLAM (Stevens and Turner, 1974). It was reported that laminated veneer lumbers compared to solid wood materials are preferred in producing furniture, especially for framework materials of wardrobes, tables, chairs and shelves (Eckelman, 1993). Fire retardants for wood change the combustion properties of wood to decrease surface flame spread. When the surface of wood material used in buildings is exposed to fire, carbonization occurs. The carbonised parts of wood act like an isolation material and this protects the wood from burning or decreases the degree of destruction occurred by the fire. Wood material which is covered by carbon, during the fire is damaged less than steel material in the same conditions (White, 1988). Wood and wood-based materials are consisted of hydrogen and carbon. When heated, wood burns by producing flammable that may ignite. The temperature has to be increased up to 275 ◦ C for the wood to be burning by itself. From this point of view, impregnation of the wood material with chemicals in many usage areas is necessary to increase the resistance of wood material against fire (Le Van and Winandy, 1990). However, if there is a flame, it can become flammable at lower temperatures. It is not possible enough to protect small dimensioned wood materials at high temperatures, because small dimensioned wood materials dry quicker than big dimensioned wood and they reach burning heat earlier. To increase the fire-retardant up to suitable level is possible with chemical protection process increasing the combustion resistance. Therefore, it is reported that inorganic salts as ammonium sulfates, ammonium phosphates, borax and zinc chloride should be used for this purpose (Williams and Mauldin, 1986). Boron compounds are well known preservative impregnations for wood materials. It was determined that commonly used impregnation materials to protect woods or wood-based panels from fire were boric acid, ammonium phosphate and borax, ammonium sulfate and chloride, zinc chloride and borate, phosphoric acid, dicyanodiamide and sodium borate (Maloney, 1977; Kozlowski et al., 1995). In recently, some mechanisms by which chemicals fire retardancy were proposed and discussed.
4 7 8 8 8
Fire properties (flame sourced and self-burning) of threelayered laminated veneer produced from small-leafed lime wood were researched. Small-leafed lime was used in outer layers and fir, white mulberry, white oak and Scotch pine woods were used in inner layers. LVL samples were produced by bonding with PVAc adhesive according to the principles of ASTM-E 69 standards. As a result; it was reported that the highest weight-loss (32.17 g), amount of CO (3754.12 ppm) and amount of CO2 (4–5%) were found in the inner layer of white oak wood, the highest amount of O2 (19.53) was found in the inner layer of white mulberry wood, the highest amount of temperature was found in the inner layer of Scotch pine and fir wood and the highest amount of unburnt sample and ash ¨ ¸ ifc¸i, ratio were found in three-layered lime wood (20%) (Ozc ¨ ¸ ifc¸i, 2000). Generally, impregnation mate2004; Uysal and Ozc rials have been applied by dipping or spraying concentrated borax on freshly sawn timber. The test samples prepared from Scotch pine and east beech woods were impregnated with immersion and pressurecontrolled methods using sodium sulfate, sodium tetra borate, copper sulfate, potassium nitrate, and zinc sulfate. The combustion properties of samples impregnated with immersion method were lower than the ones impregnated with pressure¨ ¸ ifc¸i, 2000). controlled method (Uysal and Ozc The aim of this study was to investigate the combustion properties according to ASTM-E 69 standards, and gas emission characteristics of LVL produced from chestnut and white oak, with Desmodur-VTKA and PVAc as adhesives. Veneers having thicknesses of 2.25, 3 and 4.5 mm were impregnated according to ASTM D 1413 standards and bonded with adhesives. The LVL samples were manufactured as two-, three- and four-layered.
2.
Materials and methods
The woods to be used as test samples, white oak (Quercus alba) having the density of 0.54 g/cm3 and chestnut (Cestanea sativa Mill.) having the density of 0.48 g/cm3 , were commercially purchased in Turkey. According to TS 345, nondeficient, proper, knotless, normally grown (reaction wood, and decay as well as insect or fungal damages) wood materials were selected (Anon., 1974). 2.1.
Impregnation chemicals
Borax and zinc chloride were prepared in this research, widely found in Turkey and effective against biotic and abiotic damage and having fire-retardant characteristic. As impregnation chemicals, borax (Na2 B4 O7 ·5H2 O) and zinc chloride (ZnCl2 ) were used for fire-retardant. The impregnation materials were provided from Raftel Chemical Co. 2.2.
Adhesives
The highest commonly used adhesive in the production of LVL was chosen as a bonding material. PVAc can be used in cold temperature
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
3
and solidifies quickly. The application of this adhesive is very easy and it does not damage tools during the cutting process. However, the mechanical resistance of PVAc adhesive decreases by increasing heat.
were acclimatized until they were stable at 20 ± 2 ◦ C and 65 ± 3% relative humidity in climate room. Later on they were cut into dimensions of 3 mm × 22 mm × 1030 mm and bonded with Desmodur-VTKA and PVAc
It loses bonding resistance capacity above 70 ◦ C. Using 180–200 g/m2 , the adhesive seems to be suitable under the condition that it is applied to only one surface. TS 386 standard procedure was used for apply-
adhesives as three-layered LVLs (9 mm × 19 mm × 1016 mm) according to procedure in ASTM-E 69 (Anon., 2007b). Ten test samples were cut for each test (control and lamina); 260 test samples were prepared in total, as in Fig. 1.
ing PVAc adhesive (Anon., 1999a). The density of PVAc adhesive should be 1.1 g/cm3 ; the viscosity 16 ± 3 MPa s, and the pH value and ash ratio should be 5 and 3%, respectively. A pressing time of 20 min for the cold process and 2 min and 80 ◦ C are recommended with 6–15% humidity for
2.5.
the jointing process. After a hot pressing process the materials should be attended until its normal temperature is reached. PVAc adhesive
The densities of wood materials used for the preparation of test samples were determined according to TS (Turkish Standards) 2471 and 2472 (Anon., 1976). For determining the air-dry density, the test sam-
was supplied from Bitlis Group, a producer firm in Izmit, Turkey (Anon., 1999b). According to the data sheet of adhesive manufacture, DesmodurVTKA is a single component polyurethane-based adhesive, which is widely used in assembly process in the furniture industry (Anon., 1999b). It is a single component, solvent free adhesive. It is used for gluing wood, metal, polyester, stone, glass, ceramic, PVC and other plastic materials. Its application is especially recommended in locations subjected to high-level humidity. Gluing process was carried out at 20 ± 2 ◦ C and 65 ± 3% relative humidity. According to the producer
Humidity and air-dry density
ples with a dimension of 20 mm × 30 mm × 30 mm were kept under the conditions of 20 ± 2 ◦ C and 65 ± 3% relative humidity until they reached a stable weight. The weights were measured with an analytic balance of ±0.01 g sensitivity. Afterwards, the dimensions were measured with a digital compass of 0.01 mm. The air-dried densities (ı12 ) of the samples were calculated with the following formula: ı12 (g/cm3 ) =
M12 V12
(3)
2
firm’s advice, adhesive is applied 180–190 g/m to the surfaces. Its viscosity is 14 ± 3 MPa s at 25 ◦ C; density 1.11 ± 0.02 g/cm3 at 20 ◦ C and it has strength in environment of below freezing temperature.
where M12 is the air-dry weight (g) and V12 is the volume (cm3 ) at airdry conditions. The samples were kept at a temperature of 103 ± 2 ◦ C in the drying oven until they reached a stable weight for the assess-
2.3.
ment of full-dry density. Then, they were weighed on an analytic balance of ±0.01 g sensitivity and their dimensions were measured
Impregnation method
For the impregnation process, the dipping process was applied for 36 h according to ASTM-D 1413 standards (Anon., 2007a). Before and after
with a compass of ±0.01 mm sensitivity. The volumes of the samples were determined by stereometric method and the densities (M0 ) were calculated by the following equation:
impregnation process, test samples were kiln dried (TS 5724) (Anon., 1988), and then the amount of retention (R, kg/m3 ) and ratio of retention (R, %) were calculated as follows R (×103 kg/m3 ) =
R (%) =
GC V
Mdi − Md × 100 Md
M0 V0
(4)
(1)
where M0 is the full-dry weight (g) and V0 is the full dry volume (cm3 ) of the wood material.
(2)
2.6.
where G = T2 − T1 , T2 is the sample weight after impregnation (kg), T1 is the sample weight before impregnation (kg), Mdi is the full dried weight after impregnation (kg), Md is the full dried weight before impregnation (kg), V is the volume of sample (m3 ), and C is the concentration of solution (%). 2.4.
ı0 (g/cm3 ) =
Preparation of test samples
Execution of the combustion test
The combustion test was performed to the principles of ASTM-E 69, however some changes were made in the stand. For this purpose, a digital balance with 0.01 g sensitivity was used for determination of weight loss of materials when they were burnt. Butane gas was used to make the ignition flame. The gas flow was kept standard with the flame 25 cm high, and the temperature was held at 1000 ◦ C. During the test, weight loss, temperature and gas (O2 , CO, SOx , NOx ) emission were measured in every 30 s. The combustion test was applied under a chimney where the airflow was drawn with a natural draft. At the beginning of
While preparing wood materials, chestnut and white oak woods were used. Woods were sliding cut as 4.5, 3 and 2.25 mm thicknesses and veneers were obtained for LVL. Then, the veneers were impregnated, where A is 4.5, 3 and 2.25 mm thicknesses, B 20 mm thickness. Before and after impregnation process; all samples were weighed on a digital balance with 0.01 g sensitivity. The oversized test samples
combustion test, a flame source was used for 4 min, then flame source was taken away and the combustion was made to continue for another 6 min. The combustion test was ended 10 min later. The relationships of various parts of the test stand can be seen in Fig. 2. Testo 300 M and XL flue gas analyzer was used for measuring concentration of the released gas (O2 , CO) emission and temperature variation. The probe
Fig. 1 – Control and lamina materials.
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where CO2 max : fuel-specific maximum CO2 value; 21%: oxygen level of air in %; O2 %: measured oxygen level in %. 2.7.
Statistical procedure
Multivariance analysis was applied to determine both the amount of retention in the prepared natural and lamine samples and the effects of impregnation material on combustion with or without flame source. Based on Duncan test’s being significant each test group was compared with each other and itself.
3.
Fig. 2 – Test stand of combustion. 1, Fire pipe; 2, electronics balance; 3, foot; 4, chimney gas analyzer; 5, thin steel wire.
was inserted into the first hole from the top of the fire tube. Technical data from the Testo 300 M and XL flue gas analyzer is as follows: Temperature measurement Measuring range Accuracy
−40 to +1200 ◦ C ±0.5 ◦ C (0–99.9 ◦ C) ± 0.5% of m.v.(from +100 ◦ C) 0.1/1 ◦ C (from +1000 ◦ C) Thermocouple, type K
Resolution Sensor
(NiCr–Ni) O2 measurement Measuring range
0–21 vol.%
Accuracy Resolution
±0.2 vol.% absolute 0.1 vol.%
Measuring procedure Response time t90
<20 s
Electrochemical measuring cell
CO measurement (with H2 compensation) Measuring range 0–8000 ppm ±20 ppm (to 400 ppm) ± 5% of m.v. (to 2000 ppm)
Accuracy
±10% of m.v. (to 8000 ppm) Response time t90
<30 s
Calculation of CO and CO2 : CO and CO2 have been calculated by Eqs. (1), (3) and (4): CO (mg/m3 ) =
21 − O2 reference × CO (ppm) × 1.25 21 − O2
(5)
where 21: oxygen level air; O2 : measured oxygen level. CO2 =
CO2 max (21% − O2 %) 21%
(6)
Results
Pecularities of the solution used in impregnation process are given in Table 1. As a result of using fresh solution in every impregnation process, there was no significant difference in the acidity and density of the solutions before and after the impregnation. The highest density was obtained with zinc chloride solution. This was due to using of Vac–Vac method and high solution density and these might have increased the ¨ ¸ ifc¸i, 2001). densities (Ozc pH of borax was 9.0 before and after impregnation; pH of zinc chloride was 6.0 before and after impregnation; density of borax was 1.060 g/cm3 before impregnation and 1.65 g/cm3 after impregnation; density of zinc chloride was 1.060 g/cm3 before impregnation and 1.060 g/cm3 after impregnation. The retention for impregnation chemicals is given in Table 2, and Figs. 3 and 4. The highest (23.06%) retention was observed in zinc chloride with chestnut samples, and the lowest (3.5%) in borax with white oak samples. The average densities of laminated wood samples, containing 12% moisture content are given in Table 3. The highest density was observed in LVL samples impregnated with ZnCl2 . According to the control samples, it is possible to say that impregnation chemicals and adhesives increase the density of LVLs. The average combustion values of impregnation chemicals are given in Table 4. The multivariance analysis applied to combustion test results obtained from the combustion tests. According to the variance analysis, the effects of adhesive type, weight loss, and temperature and gas emission were statistically significant. The interactions between LVL and impregnation chemicals were statistically important (P ≤ 0.05). The means of variation sources that were found to be significant were compared using Duncan’s test and the average values are summarized in Tables 5 and 6. According to combustion test results, the highest weight loss was obtained from chestnut wood (control sample)
Table 1 – Properties of impregnation chemicals Impregnation chemicals Borax Zinc chloride
Viscosity (20 ◦ C) 4 mm/Din Cup/sn 8 8
Solvent
Pure water Pure water
BI: before impregnation; AI: after impregnation.
Solution concentration (%) 10 10
Temperature (◦ C)
20 20
pH
Density (g/ml)
BI
AI
BI
9.0 6.0
9.0 6.0
1.060 1.070
AI 1.065 1.075
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bonded with PVAc adhesive, the lowest was obtained from four-layered chestnut wood samples bonded with D-VTKA and impregnated with borax. According to these; when the number of layers were increased, the weight loss decreased. It can be said that the increase of number of layers and the retention of impregnation chemical increase the combustion resistance of laminated wood material. The highest reduction of O2 concentration was obtained in four-layered LVL chestnut wood samples treated with borax and bonded with D-VTKA, the lowest amount of O2 was obtained in control samples. According to this; both of impregnation materials showed fire-retardant effect in LVL samples. The highest amount of CO was detected on chestnut samples impregnated with borax, the lowest was determined in chestnut control samples. Hence, the highest burning rate was observed in unimpregnated samples. As a result of moving the flame source from fire tube (4 min from the beginning of combustion), decreasing was observed in the CO ratio in impregnated samples at the stage of combus-
Fig. 3 – Comparison of wood material and retention amount of impregnation chemical.
Table 2 – Amounts and ratios of retention according to layer thickness and impregnation materials Woods
Impregnation material
Layer thickness (mm) 4.5
Zinc chloride
3
2.25 Chestnut 4.5
Borax
3
2.25
4.5
Zinc chloride
3
2.25 White oak 4.5
Borax
3
2.25
Values
Average mass (g)
S.D.
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
64.76 75.90 124.28 50.44 58.22 100.89 29.66 36.50 60.12 64.76 73.90 117.80 50.44 58.90 90.77 29.66 35.40 62.77
1.20 1.09 3.09 1.02 1.23 3.45 1.20 1.25 3.32 1.23 1.12 3.23 1.32 1.32 3.45 1.22 1.23 3.56
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
181.12 190.23 220.34 106.60 113.89 142.00 91.33 96.30 132.90 181.12 187.56 211.89 106.60 112.66 140.89 91.33 94.90 130.36
1.45 1.67 3.89 1.90 1.98 3.00 1.98 1.45 3.87 1.89 1.96 3.89 1.90 2.07 3.07 1.08 1.24 2.01
Average retention (kg/m3 )
Average retention (%)
12.86
17.20
13.43
15.42
15.74
23.06
10.50
14.11
14.60
16.77
13.21
19.49
10.48
5.03
12.08
6.5
11.44
5.4
7.41
3.5
10.3
5.6
8.21
3.9
Value 1: full dry mass before impregnation (g); value 2: full dry mass after impregnation (g); value 3: full damp mass after impregnation (g); S.D.: standard deviation.
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tion without a flame source. As for control samples, there was important change in CO ratio because of proceeding combustion without a flame source. According to the control samples, impregnation chemicals decreased the existence of CO by diminishing the combustion. At a very high temperature no oxygen reaches the carbon therefore it burns in CO2 according to the following reaction equation: C + CO2 → 2CO
(7)
The highest temperature variation (398.5 ◦ C) was observed in white oak LVL samples. The lowest was measured in chestnut LVL samples impregnated with sodium tetra borate. At the first stage of combustion, an increase in temperature occurred due to the flame source as well as a decrease as
Fig. 4 – Proportions of retention relating to wood and impregnation material.
Table 3 – Densities of LVL samples (g/cm3 ) Adhesives
Impregnation
Layer
ı12 (white oak)
2 3 4 2 3 4
0.67 0.70 0.74 0.81 0.70 0.75 0.84
0.61 0.64 0.69 0.75 0.65 0.70 0.78
2 3 4 2 3 4
0.68 0.71 0.76 0.83 0.72 0.77 0.87
0.64 0.68 0.71 0.76 0.67 0.74 0.79
Control Borax PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
ı12 (chestnut)
Table 4 – The gas emission and mass loss values in the combustion test Adhesive Impregnation type material
Layer (mm)
White oak Mass loss (g)
–
Control Borax Zinc chloride Control Borax
PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
O2 (%) CO (ppm)
Chestnut Temperature (◦ C)
Mass loss (g)
O2 (%) CO (ppm)
Temperature (◦ C)
– – –
32.4 5.5 6.7
16.2 18.0 18.0
1430.5 133.6 311.1
393.2 95.4 149.8
36.3 6.7 9.4
16.3 18.8 18.3
1330.0 100.9 418.1
344.1 95.4 134.3
– 2 3 4 2 3 4
35.2 4.3 10.39 3.7 19.8 8.5 4.5
16.7 19.3 18.5 20.0 17.3 18.4 20.1
1132.4 121.6 983.3 806.7 2539.6 2834.7 115.1
224.2 95.4 224.9 82.5 256.8 205.6 62.9
43.1 8.6 6.5 10.5 9.3 10.1 7.8
16.3 18.6 19.8 19.2 19.2 19.2 19.6
1010.1 614.9 333.1 271.7 614.2 681.2 178.7
313.6 169.5 122.7 173.8 169.5 193.1 78.0
– 2 3 4 2 3 4
30.6 10.2 10.2 1.5 3.1 12.7 3.5
16.1 17.7 19.3 20.0 20.0 17.3 19.7
2711.5 955.6 958.6 229.7 210.3 218.8 212.4
398.5 309.3 322.3 99.2 89.2 300.2 89.8
40.0 10.0 15.1 9.4 6.9 13.9 7.0
17.3 19.3 18.2 18.4 19.9 17.3 18.0
2190.9 294.9 1144.0 234.7 455.5 2482.9 634.1
262.8 145.3 235.7 178.7 101.6 291.5 161.6
7
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
Table 5 – The average values of combustion tests Wood material (adhesive type vs. impregnation material)
O2 (%)
S.D.
Foura -layered chestnut (D-VTKA–borax) Four-layered chestnut (PVAc–borax) Four-layered white oak (D-VTKA–borax) Four-layered white oak (PVAc–borax) Four-layered chestnut (D-VTKA–zinc chloride) Four-layered chestnut (PVAc–zinc chloride) Three-layered white oak (D-VTKA–borax) Four-layered white oak (PVAc–zinc chloride) Four-layered white oak (D-VTKA–zinc chloride) Three-layered chestnut (PVAc–borax) Two-layered chestnut (PVAc–zinc chloride) Two-layered chestnut (PVAc–borax) Three-layered chestnut (PVAc–zinc chloride) Three-layered white oak (PVAc–borax) Three-layered white oak (PVAc–zinc chloride) Three-layered chestnut (D-VTKA–borax) Two-layered chestnut (D-VTKA–borax) Two-layered white oak (D-VTKA–borax) Two-layered white oak (PVAc–borax) Two-layered white oak (PVAc–zinc chloride) Three-layered white oak (D-VTKA–zinc chloride) Chestnut (D-VTKA–control) Three-layered chestnut (D-VTKA–zinc chloride) Two-layered chestnut (D-VTKA–zinc chloride) Two-layered white oak (D-VTKA–zinc chloride) White oak (PVAc–control) Chestnut (PVAc–control) White oak (D-VTKA–control)
20.4
1.1
20.2
a
HG
CO (ppm)
S.D.
HG
Ash rate (%)
S.D.
HG
Temperature (◦ C)
A
2834.7
2.2
A
18.1
2.3
H
78.7
2.2
E
1.3
A
2271.5
3.1
B
22.7
1.6
G
73.8
2.3
E
20.0
1.5
A
2132.4
3.1
B
28.1
2.5
G
99.2
2.5
E
19.9
1.2
B
2135.9
4.5
B
28.0
2.2
G
82.5
1.4
E
19.8
1.3
B
1482.9
3.2
C
40.7
1.5
E
161.6
2.3
D
19.6
1.4
B
1190.9
2.3
D
31.3
2.4
F
148.0
3.4
D
19.3
1.2
B
1188.8
3.5
D
34.2
2.2
F
122.3
1.4
D
19.1
1.4
B
1115.1
3.4
D
44.3
1.7
E
162.9
2.4
D
19.1
1.3
B
1330.0
2.3
C
40.2
2.3
E
189.8
1.5
D
19.0
1.4
B
1634.1
2.6
C
30.7
1.6
F
122.7
2.4
D
18.6
1.2
C
844.0
3.2
F
47.1
2.2
E
169.5
2.2
D
18.6 18.5
1.3 1.2
C C
894.9 844.0
4.3 3.4
F F
49.5 40.4
2.3 1.4
E E
169.5 193.1
45.3 3.6
D D
18.5
1.2
C
1033.1
4.2
D
36.0
3.2
F
124.9
5.2
D
18.4
1.4
C
983.3
3.4
E
52.8
2.4
D
205.6
3.2
C
18.2
1.3
C
1214.9
4.3
C
27.7
2.3
G
135.7
5.3
D
18.1
1.2
C
455.5
3.2
K
39.6
1.7
F
145.3
3.1
D
17.7
1.4
D
418.1
3.4
K
56.2
1.6
D
209.3
4.4
C
17.3
1.3
D
521.6
3.3
I
51.7
1.3
D
195.4
3.7
D
17.3
1.2
D
844.0
3.2
F
52.8
1.4
D
256.8
3.6
C
17.3
1.5
D
710.1
4.5
G
48.1
2.5
E
200.2
3.5
C
17.3 17.3
1.2 1.4
D D
806.7 982.9
4.2 4.4
O E
80.4 45.1
2.2 2.4
A E
262.8 201.5
4.5 3.4
C C
16.9
1.2
E
271.7
3.2
M
56.8
2.3
D
201.6
3.3
C
16.8
1.4
E
355.6
2.4
L
51.8
2.5
D
289.2
2.5
C
16.7 16.3 16.1
1.2 1.2 1.4
E E E
121.6 210.3 153.6
2.2 3.2 3.4
N P N
69.1 74.8 82.4
2.3 2.4 2.6
C B A
324.2 313.6 398.5
3.3 3.2 3.5
B B A
S.D.
HG
Number of layers.
a result of getting far away of the flame source from fire tube ¨ ¸ ifc¸i, 2005). The highest concentration of SO2 was (Uysal and Ozc observed in zinc chloride (1.43 ppm) impregnated LVL samples, the highest increase in NOx concentration was observed in white oak control samples (1.27 ppm). However, the temperature did not go up to 1000 ◦ C, so SO2 and NOx were not thoroughly observed.
4.
Discussions
There were no significant changes in pH values and densities of solutions before and after impregnation. This was due to the use of a fresh solvent for each impregnation variation. For amount of retention, zinc chloride solution had the
8
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
Table 6 – Combustion ratios according to the first mass (%) Adhesive type
Impregnation material
Control Borax PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
Number of layers (mm)
White oak First mass (g)
Last mass (g)
– 2 3 4 2 3 4
145.7 165.7 161.1 175.8 170.3 175.2 160.5
45.0 80.0 100.8 126.4 69.2 65.0 89.4
– 2 3 4 2 3 4
140.7 149.8 145.7 146.4 145.9 142.1 165.2
25.3 89.6 95.8 90.5 70.3 70.8 75.2
highest value; this could be due to its high-density value ¨ ¸ ifc¸i, 2001). Obtaining high retention value according to (Ozc wood type and laminated layer thickness could be because chestnut had lower density compared to white oak. Sapwood of chestnut has narrow cross-section, and trachee diameters of chestnut is wider, although yearly rings of both wood materials have large trachee (Bozkurt and Erdin, 1997). And these might have increased the retention ratio of impregnation material. At the end of combustion test, the highest weight loss was found in chestnut wood control samples, the lowest was found in four-layered laminated chestnut samples bonded with DVTKA adhesive. LVL having high number of layers might have blocked the fire. The amount of O2 did not get lower; because of that there was not any combustion. Higher amount of CO comes out if there is not full combustion. The temperature might have got a bit higher because of anatomical structure of white oak wood having extractive materials. The highest amount of unburnt piece and ash ratio was found amongst white oak wood control samples, and the lowest in fourlayered laminated chestnut samples treated with borax and bonded with D-VTKA adhesive. It was reported in the literature that the temperature must be increased up to 275 ◦ C for the wood burning itself. So, it is necessary for wood material to be impregnated with chemical materials in order to increase the resistance of wood against fire (Le Van and Winandy, 1990). In another study; it was determined that boric acid, ammonium phosphate and borax, ammonium sulfate and chloride, zinc chloride and borate, phosphoric acid, dicyanodiamide sodium borate were commonly used materials to protect wood and composite materials from fire (Maloney, 1977).
5.
Conclusions
As a result, borax was found to be an effective fire-retardant chemical in LVL produced from chestnut bonded with PVAc adhesive. In other words, borax reduces combustion of LVL. It
Chestnut
Amount of combustion (%)
First mass (g)
Last mass (g)
Amount of combustion (%)
69.11 51.71 36.05 28.01 59.34 52.89 44.38
103.0 121.3 116.4 110.1 115.7 118.7 130.0
25.9 61.2 80.6 85.1 61.2 70.7 89.2
74.85 49.54 30.75 22.70 47.10 40.43 31.38
82.46 56.20 34.20 28.15 51.81 48.17 40.20
97.5 110.9 104.6 110.8 103.4 100.9 104.2
19.1 66.9 75.6 90.7 65.3 75. 61.7
80.41 39.67 27.72 18.14 56.84 45.17 40.78
can be said that the usage life of the material can get longer if they are bonded with PVAc adhesive. LVL produced from chestnut wood should especially be impregnated with borax or zinc chloride in case it is exposed to fire. This decreases the usage of forest sources and supports the national economy.
Acknowledgement This study was made as MSc Thesis by Oktay OKC ¸ U in the Graduate School of Natural and Applied Sciences, Zonguldak Karaelmas University, Zonguldak 2006 (in Turkish).
references
Anon., 1974. TS 345, Operation Methods for the Effect of Wood Impregnation Materials. Turkish Standard Institute. Anon., 1976. TS 2472, Unit Volume Weight for Physical and Mechanical Tests. Turkish Standard Institute, Ankara. Anon., 1988. TS 5724, Wood Protection—Determination of Boron, Copper, Chrome and Arsenic Quantities in Impregnated Wood and Impregnation Materials Solving in Water-Volumetric Method. Turkish Standard Institute. Anon., 1999. TS En 386, Bonded Laminated Wood—Performance and Military Production Conditions. Turkish Standard Institute. Anon., 1999. Producer Firm Text, Polisan Dilovası-Gebze. Instruction Manuel. Kocaeli, Turkey. Anon., 2007. ASTM-D 1413-07, Standard test method for wood preservatives by laboratory soil-block culture. Annual Book of ASTM Standards. ASTM Standards, West Conshohocken, PA, USA. Anon., 2007. ASTM E 69-02, Standard Test Method for Combustible Properties of Treated Wood by the Fire-Tube Apparatus. ASTM Standards, USA. Bozkurt, Y., Erdin, N., 1997. Wood Technology, Istanbul University. Forest Faculty Publication, Turkey, pp. 237–345. Eckelman, C.A., 1993. Potential uses of laminated veneer lumber in furniture. Forest Product J. 43, 19–24. Kozlowski, R., Helwig, M., Przepiera, A., 1995. Light-weight, environmentally friendly, fire retardant composite, board for
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
panelling and construction. Inorg. Bonded Wood Fiber Compos. Mater., 6–11. Le Van, S.L., Winandy, J.E., 1990. Effects of fire retardant treatments on wood strength: a review. Wood Fiber Sci. 22, 13–131. Maloney, T.M., 1977. Modern Particleboard and Dry-Process Fiberboard Manufacturing. Miller Greeman Publishes, Sanfrancisco, pp. 13–15. ¨ ¸ ifc¸i, A., 2001. Technological characteristics of impregnated Ozc laminated wood materials. PhD Thesis. G.U. Institute of Science, Ankara. ¨ ¸ ifc¸i, A., 2004. Combustion properties of laminated veneer Ozc lumber of Calabrian pine after impregnating. Teknoloji 7 (1–2), 1–11.
9
Stevens, W.C., Turner, N., 1974. Wood Bending Handbook, UK, pp. 90–94. ¨ ¸ ifc¸i, A., 2000. Combustion properties of laminated Uysal, B., Ozc wood material produced with PVAc adhesive from lime wood (Morus alba L.). J. Gazi Univ. Sci. Inst. 13 (4), 1023–1035. ¨ ¸ ifc¸i, A., 2005. Combustion properties of laminated Uysal, B., Ozc veneer lumbers bonded with polyvinyl acetate and phenol formaldehyde adhesives and impregnated with some chemicals. Combust. Sci. Tech. 177, 1253–1271. White, R.H., 1988. Analytical methods for determining for resistance timber members the SFPE. Hand Book of Fire Protection Engineering, vol. 8. Wood Sci. and Tech, pp.133–142. Williams, L.H., Mauldin, J.K., 1986. Integrated protection against lyctid beetloe infectations. Forest Product J. 36, 11–28.
journal homepage: www.elsevier.com/locate/jmatprotec
Review
Impacts of some chemicals on combustion properties of impregnated laminated veneer lumber (LVL) ¨ ¸ ifc¸i a,∗ , Oktay Okc¸u b Ayhan Ozc a b
¨ University, Technical Education Faculty, 78050 Karabuk, ¨ Turkey Karabuk Cumhuriyet University, Akdagmadeni College, 66300 Yozgat, Turkey
a r t i c l e
i n f o
a b s t r a c t
Article history:
The objective of this study was to investigate the effects of zinc chloride (ZnCl2 ) and borax
Received 27 May 2007
(Na2 B4 O7 ·5H2 O) on combustion properties of laminated veneer lumbers (LVLs) with two,
Received in revised form
three and four-layered, produced from white oak (Quercus alba) and chestnut (Cestanea sativa
27 September 2007
Mill.) woods. Veneers obtained for LVL were impregnated according to ASTM-D 1413. Veneers
Accepted 8 October 2007
applied vacuum method were dried and bonded with poly(vinyl) acetate (PVAc) and D-VTKA polyurethane-based adhesives. The combustion test was performed according to the procedure defined in the ASTM-E 69 standard. The results indicated that the highest weight
Keywords:
loss of LVL (43.1 g) was observed in unprocessed weigh wood samples. The lowest O2 con-
LVL
sumption ratio was in borax-impregnated LVL samples with Desmodur-VTKA, with a ratio
Impregnation
20.4%. The highest CO ratio observed in LVL control samples was 2834.7 ppm, the highest
Combustion
temperature measured in borax-impregnated control LVL was 398.5 ◦ C, the highest ash ratio
Zinc chloride
was measured as 82.4%, however NOx and SOx emissions (oxides of nitrogen and sulfur) could not be measured, because heat did not go up to 1000 ◦ C. As a result, borax was found
Borax
to be an effective fire-retardant chemical in LVL. In conclusion, it can be recommended as a fire-retardant building material. © 2007 Elsevier B.V. All rights reserved.
Contents 1. 2.
∗
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Impregnation chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Adhesives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. Impregnation method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. Preparation of test samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5. Humidity and air-dry density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6. Execution of the combustion test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7. Statistical procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Corresponding author. Tel.: +90 370 433 82 00; fax: +90 370 433 82 04. ¨ ¸ ifc¸i). E-mail address: [email protected] (A. Ozc 0924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.10.003
2 2 2 2 3 3 3 3 4
2
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
3. 4. 5.
1.
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction
Laminated wood materials are named differently according to the layer thicknesses used. A material having a thickness of 25.4–50.8 mm used in producing large dimensioned laminated solid wood material which is used in building sector and it is named as glued-laminated lumber (GLULAM). The veneer with a thickness of 3.2 mm is used in producing small-sized laminated solid materials and those kind of laminated materials are named as laminated veneer lumber (LVL) or MICROLAM (Stevens and Turner, 1974). It was reported that laminated veneer lumbers compared to solid wood materials are preferred in producing furniture, especially for framework materials of wardrobes, tables, chairs and shelves (Eckelman, 1993). Fire retardants for wood change the combustion properties of wood to decrease surface flame spread. When the surface of wood material used in buildings is exposed to fire, carbonization occurs. The carbonised parts of wood act like an isolation material and this protects the wood from burning or decreases the degree of destruction occurred by the fire. Wood material which is covered by carbon, during the fire is damaged less than steel material in the same conditions (White, 1988). Wood and wood-based materials are consisted of hydrogen and carbon. When heated, wood burns by producing flammable that may ignite. The temperature has to be increased up to 275 ◦ C for the wood to be burning by itself. From this point of view, impregnation of the wood material with chemicals in many usage areas is necessary to increase the resistance of wood material against fire (Le Van and Winandy, 1990). However, if there is a flame, it can become flammable at lower temperatures. It is not possible enough to protect small dimensioned wood materials at high temperatures, because small dimensioned wood materials dry quicker than big dimensioned wood and they reach burning heat earlier. To increase the fire-retardant up to suitable level is possible with chemical protection process increasing the combustion resistance. Therefore, it is reported that inorganic salts as ammonium sulfates, ammonium phosphates, borax and zinc chloride should be used for this purpose (Williams and Mauldin, 1986). Boron compounds are well known preservative impregnations for wood materials. It was determined that commonly used impregnation materials to protect woods or wood-based panels from fire were boric acid, ammonium phosphate and borax, ammonium sulfate and chloride, zinc chloride and borate, phosphoric acid, dicyanodiamide and sodium borate (Maloney, 1977; Kozlowski et al., 1995). In recently, some mechanisms by which chemicals fire retardancy were proposed and discussed.
4 7 8 8 8
Fire properties (flame sourced and self-burning) of threelayered laminated veneer produced from small-leafed lime wood were researched. Small-leafed lime was used in outer layers and fir, white mulberry, white oak and Scotch pine woods were used in inner layers. LVL samples were produced by bonding with PVAc adhesive according to the principles of ASTM-E 69 standards. As a result; it was reported that the highest weight-loss (32.17 g), amount of CO (3754.12 ppm) and amount of CO2 (4–5%) were found in the inner layer of white oak wood, the highest amount of O2 (19.53) was found in the inner layer of white mulberry wood, the highest amount of temperature was found in the inner layer of Scotch pine and fir wood and the highest amount of unburnt sample and ash ¨ ¸ ifc¸i, ratio were found in three-layered lime wood (20%) (Ozc ¨ ¸ ifc¸i, 2000). Generally, impregnation mate2004; Uysal and Ozc rials have been applied by dipping or spraying concentrated borax on freshly sawn timber. The test samples prepared from Scotch pine and east beech woods were impregnated with immersion and pressurecontrolled methods using sodium sulfate, sodium tetra borate, copper sulfate, potassium nitrate, and zinc sulfate. The combustion properties of samples impregnated with immersion method were lower than the ones impregnated with pressure¨ ¸ ifc¸i, 2000). controlled method (Uysal and Ozc The aim of this study was to investigate the combustion properties according to ASTM-E 69 standards, and gas emission characteristics of LVL produced from chestnut and white oak, with Desmodur-VTKA and PVAc as adhesives. Veneers having thicknesses of 2.25, 3 and 4.5 mm were impregnated according to ASTM D 1413 standards and bonded with adhesives. The LVL samples were manufactured as two-, three- and four-layered.
2.
Materials and methods
The woods to be used as test samples, white oak (Quercus alba) having the density of 0.54 g/cm3 and chestnut (Cestanea sativa Mill.) having the density of 0.48 g/cm3 , were commercially purchased in Turkey. According to TS 345, nondeficient, proper, knotless, normally grown (reaction wood, and decay as well as insect or fungal damages) wood materials were selected (Anon., 1974). 2.1.
Impregnation chemicals
Borax and zinc chloride were prepared in this research, widely found in Turkey and effective against biotic and abiotic damage and having fire-retardant characteristic. As impregnation chemicals, borax (Na2 B4 O7 ·5H2 O) and zinc chloride (ZnCl2 ) were used for fire-retardant. The impregnation materials were provided from Raftel Chemical Co. 2.2.
Adhesives
The highest commonly used adhesive in the production of LVL was chosen as a bonding material. PVAc can be used in cold temperature
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
3
and solidifies quickly. The application of this adhesive is very easy and it does not damage tools during the cutting process. However, the mechanical resistance of PVAc adhesive decreases by increasing heat.
were acclimatized until they were stable at 20 ± 2 ◦ C and 65 ± 3% relative humidity in climate room. Later on they were cut into dimensions of 3 mm × 22 mm × 1030 mm and bonded with Desmodur-VTKA and PVAc
It loses bonding resistance capacity above 70 ◦ C. Using 180–200 g/m2 , the adhesive seems to be suitable under the condition that it is applied to only one surface. TS 386 standard procedure was used for apply-
adhesives as three-layered LVLs (9 mm × 19 mm × 1016 mm) according to procedure in ASTM-E 69 (Anon., 2007b). Ten test samples were cut for each test (control and lamina); 260 test samples were prepared in total, as in Fig. 1.
ing PVAc adhesive (Anon., 1999a). The density of PVAc adhesive should be 1.1 g/cm3 ; the viscosity 16 ± 3 MPa s, and the pH value and ash ratio should be 5 and 3%, respectively. A pressing time of 20 min for the cold process and 2 min and 80 ◦ C are recommended with 6–15% humidity for
2.5.
the jointing process. After a hot pressing process the materials should be attended until its normal temperature is reached. PVAc adhesive
The densities of wood materials used for the preparation of test samples were determined according to TS (Turkish Standards) 2471 and 2472 (Anon., 1976). For determining the air-dry density, the test sam-
was supplied from Bitlis Group, a producer firm in Izmit, Turkey (Anon., 1999b). According to the data sheet of adhesive manufacture, DesmodurVTKA is a single component polyurethane-based adhesive, which is widely used in assembly process in the furniture industry (Anon., 1999b). It is a single component, solvent free adhesive. It is used for gluing wood, metal, polyester, stone, glass, ceramic, PVC and other plastic materials. Its application is especially recommended in locations subjected to high-level humidity. Gluing process was carried out at 20 ± 2 ◦ C and 65 ± 3% relative humidity. According to the producer
Humidity and air-dry density
ples with a dimension of 20 mm × 30 mm × 30 mm were kept under the conditions of 20 ± 2 ◦ C and 65 ± 3% relative humidity until they reached a stable weight. The weights were measured with an analytic balance of ±0.01 g sensitivity. Afterwards, the dimensions were measured with a digital compass of 0.01 mm. The air-dried densities (ı12 ) of the samples were calculated with the following formula: ı12 (g/cm3 ) =
M12 V12
(3)
2
firm’s advice, adhesive is applied 180–190 g/m to the surfaces. Its viscosity is 14 ± 3 MPa s at 25 ◦ C; density 1.11 ± 0.02 g/cm3 at 20 ◦ C and it has strength in environment of below freezing temperature.
where M12 is the air-dry weight (g) and V12 is the volume (cm3 ) at airdry conditions. The samples were kept at a temperature of 103 ± 2 ◦ C in the drying oven until they reached a stable weight for the assess-
2.3.
ment of full-dry density. Then, they were weighed on an analytic balance of ±0.01 g sensitivity and their dimensions were measured
Impregnation method
For the impregnation process, the dipping process was applied for 36 h according to ASTM-D 1413 standards (Anon., 2007a). Before and after
with a compass of ±0.01 mm sensitivity. The volumes of the samples were determined by stereometric method and the densities (M0 ) were calculated by the following equation:
impregnation process, test samples were kiln dried (TS 5724) (Anon., 1988), and then the amount of retention (R, kg/m3 ) and ratio of retention (R, %) were calculated as follows R (×103 kg/m3 ) =
R (%) =
GC V
Mdi − Md × 100 Md
M0 V0
(4)
(1)
where M0 is the full-dry weight (g) and V0 is the full dry volume (cm3 ) of the wood material.
(2)
2.6.
where G = T2 − T1 , T2 is the sample weight after impregnation (kg), T1 is the sample weight before impregnation (kg), Mdi is the full dried weight after impregnation (kg), Md is the full dried weight before impregnation (kg), V is the volume of sample (m3 ), and C is the concentration of solution (%). 2.4.
ı0 (g/cm3 ) =
Preparation of test samples
Execution of the combustion test
The combustion test was performed to the principles of ASTM-E 69, however some changes were made in the stand. For this purpose, a digital balance with 0.01 g sensitivity was used for determination of weight loss of materials when they were burnt. Butane gas was used to make the ignition flame. The gas flow was kept standard with the flame 25 cm high, and the temperature was held at 1000 ◦ C. During the test, weight loss, temperature and gas (O2 , CO, SOx , NOx ) emission were measured in every 30 s. The combustion test was applied under a chimney where the airflow was drawn with a natural draft. At the beginning of
While preparing wood materials, chestnut and white oak woods were used. Woods were sliding cut as 4.5, 3 and 2.25 mm thicknesses and veneers were obtained for LVL. Then, the veneers were impregnated, where A is 4.5, 3 and 2.25 mm thicknesses, B 20 mm thickness. Before and after impregnation process; all samples were weighed on a digital balance with 0.01 g sensitivity. The oversized test samples
combustion test, a flame source was used for 4 min, then flame source was taken away and the combustion was made to continue for another 6 min. The combustion test was ended 10 min later. The relationships of various parts of the test stand can be seen in Fig. 2. Testo 300 M and XL flue gas analyzer was used for measuring concentration of the released gas (O2 , CO) emission and temperature variation. The probe
Fig. 1 – Control and lamina materials.
4
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
where CO2 max : fuel-specific maximum CO2 value; 21%: oxygen level of air in %; O2 %: measured oxygen level in %. 2.7.
Statistical procedure
Multivariance analysis was applied to determine both the amount of retention in the prepared natural and lamine samples and the effects of impregnation material on combustion with or without flame source. Based on Duncan test’s being significant each test group was compared with each other and itself.
3.
Fig. 2 – Test stand of combustion. 1, Fire pipe; 2, electronics balance; 3, foot; 4, chimney gas analyzer; 5, thin steel wire.
was inserted into the first hole from the top of the fire tube. Technical data from the Testo 300 M and XL flue gas analyzer is as follows: Temperature measurement Measuring range Accuracy
−40 to +1200 ◦ C ±0.5 ◦ C (0–99.9 ◦ C) ± 0.5% of m.v.(from +100 ◦ C) 0.1/1 ◦ C (from +1000 ◦ C) Thermocouple, type K
Resolution Sensor
(NiCr–Ni) O2 measurement Measuring range
0–21 vol.%
Accuracy Resolution
±0.2 vol.% absolute 0.1 vol.%
Measuring procedure Response time t90
<20 s
Electrochemical measuring cell
CO measurement (with H2 compensation) Measuring range 0–8000 ppm ±20 ppm (to 400 ppm) ± 5% of m.v. (to 2000 ppm)
Accuracy
±10% of m.v. (to 8000 ppm) Response time t90
<30 s
Calculation of CO and CO2 : CO and CO2 have been calculated by Eqs. (1), (3) and (4): CO (mg/m3 ) =
21 − O2 reference × CO (ppm) × 1.25 21 − O2
(5)
where 21: oxygen level air; O2 : measured oxygen level. CO2 =
CO2 max (21% − O2 %) 21%
(6)
Results
Pecularities of the solution used in impregnation process are given in Table 1. As a result of using fresh solution in every impregnation process, there was no significant difference in the acidity and density of the solutions before and after the impregnation. The highest density was obtained with zinc chloride solution. This was due to using of Vac–Vac method and high solution density and these might have increased the ¨ ¸ ifc¸i, 2001). densities (Ozc pH of borax was 9.0 before and after impregnation; pH of zinc chloride was 6.0 before and after impregnation; density of borax was 1.060 g/cm3 before impregnation and 1.65 g/cm3 after impregnation; density of zinc chloride was 1.060 g/cm3 before impregnation and 1.060 g/cm3 after impregnation. The retention for impregnation chemicals is given in Table 2, and Figs. 3 and 4. The highest (23.06%) retention was observed in zinc chloride with chestnut samples, and the lowest (3.5%) in borax with white oak samples. The average densities of laminated wood samples, containing 12% moisture content are given in Table 3. The highest density was observed in LVL samples impregnated with ZnCl2 . According to the control samples, it is possible to say that impregnation chemicals and adhesives increase the density of LVLs. The average combustion values of impregnation chemicals are given in Table 4. The multivariance analysis applied to combustion test results obtained from the combustion tests. According to the variance analysis, the effects of adhesive type, weight loss, and temperature and gas emission were statistically significant. The interactions between LVL and impregnation chemicals were statistically important (P ≤ 0.05). The means of variation sources that were found to be significant were compared using Duncan’s test and the average values are summarized in Tables 5 and 6. According to combustion test results, the highest weight loss was obtained from chestnut wood (control sample)
Table 1 – Properties of impregnation chemicals Impregnation chemicals Borax Zinc chloride
Viscosity (20 ◦ C) 4 mm/Din Cup/sn 8 8
Solvent
Pure water Pure water
BI: before impregnation; AI: after impregnation.
Solution concentration (%) 10 10
Temperature (◦ C)
20 20
pH
Density (g/ml)
BI
AI
BI
9.0 6.0
9.0 6.0
1.060 1.070
AI 1.065 1.075
5
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bonded with PVAc adhesive, the lowest was obtained from four-layered chestnut wood samples bonded with D-VTKA and impregnated with borax. According to these; when the number of layers were increased, the weight loss decreased. It can be said that the increase of number of layers and the retention of impregnation chemical increase the combustion resistance of laminated wood material. The highest reduction of O2 concentration was obtained in four-layered LVL chestnut wood samples treated with borax and bonded with D-VTKA, the lowest amount of O2 was obtained in control samples. According to this; both of impregnation materials showed fire-retardant effect in LVL samples. The highest amount of CO was detected on chestnut samples impregnated with borax, the lowest was determined in chestnut control samples. Hence, the highest burning rate was observed in unimpregnated samples. As a result of moving the flame source from fire tube (4 min from the beginning of combustion), decreasing was observed in the CO ratio in impregnated samples at the stage of combus-
Fig. 3 – Comparison of wood material and retention amount of impregnation chemical.
Table 2 – Amounts and ratios of retention according to layer thickness and impregnation materials Woods
Impregnation material
Layer thickness (mm) 4.5
Zinc chloride
3
2.25 Chestnut 4.5
Borax
3
2.25
4.5
Zinc chloride
3
2.25 White oak 4.5
Borax
3
2.25
Values
Average mass (g)
S.D.
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
64.76 75.90 124.28 50.44 58.22 100.89 29.66 36.50 60.12 64.76 73.90 117.80 50.44 58.90 90.77 29.66 35.40 62.77
1.20 1.09 3.09 1.02 1.23 3.45 1.20 1.25 3.32 1.23 1.12 3.23 1.32 1.32 3.45 1.22 1.23 3.56
1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3
181.12 190.23 220.34 106.60 113.89 142.00 91.33 96.30 132.90 181.12 187.56 211.89 106.60 112.66 140.89 91.33 94.90 130.36
1.45 1.67 3.89 1.90 1.98 3.00 1.98 1.45 3.87 1.89 1.96 3.89 1.90 2.07 3.07 1.08 1.24 2.01
Average retention (kg/m3 )
Average retention (%)
12.86
17.20
13.43
15.42
15.74
23.06
10.50
14.11
14.60
16.77
13.21
19.49
10.48
5.03
12.08
6.5
11.44
5.4
7.41
3.5
10.3
5.6
8.21
3.9
Value 1: full dry mass before impregnation (g); value 2: full dry mass after impregnation (g); value 3: full damp mass after impregnation (g); S.D.: standard deviation.
6
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
tion without a flame source. As for control samples, there was important change in CO ratio because of proceeding combustion without a flame source. According to the control samples, impregnation chemicals decreased the existence of CO by diminishing the combustion. At a very high temperature no oxygen reaches the carbon therefore it burns in CO2 according to the following reaction equation: C + CO2 → 2CO
(7)
The highest temperature variation (398.5 ◦ C) was observed in white oak LVL samples. The lowest was measured in chestnut LVL samples impregnated with sodium tetra borate. At the first stage of combustion, an increase in temperature occurred due to the flame source as well as a decrease as
Fig. 4 – Proportions of retention relating to wood and impregnation material.
Table 3 – Densities of LVL samples (g/cm3 ) Adhesives
Impregnation
Layer
ı12 (white oak)
2 3 4 2 3 4
0.67 0.70 0.74 0.81 0.70 0.75 0.84
0.61 0.64 0.69 0.75 0.65 0.70 0.78
2 3 4 2 3 4
0.68 0.71 0.76 0.83 0.72 0.77 0.87
0.64 0.68 0.71 0.76 0.67 0.74 0.79
Control Borax PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
ı12 (chestnut)
Table 4 – The gas emission and mass loss values in the combustion test Adhesive Impregnation type material
Layer (mm)
White oak Mass loss (g)
–
Control Borax Zinc chloride Control Borax
PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
O2 (%) CO (ppm)
Chestnut Temperature (◦ C)
Mass loss (g)
O2 (%) CO (ppm)
Temperature (◦ C)
– – –
32.4 5.5 6.7
16.2 18.0 18.0
1430.5 133.6 311.1
393.2 95.4 149.8
36.3 6.7 9.4
16.3 18.8 18.3
1330.0 100.9 418.1
344.1 95.4 134.3
– 2 3 4 2 3 4
35.2 4.3 10.39 3.7 19.8 8.5 4.5
16.7 19.3 18.5 20.0 17.3 18.4 20.1
1132.4 121.6 983.3 806.7 2539.6 2834.7 115.1
224.2 95.4 224.9 82.5 256.8 205.6 62.9
43.1 8.6 6.5 10.5 9.3 10.1 7.8
16.3 18.6 19.8 19.2 19.2 19.2 19.6
1010.1 614.9 333.1 271.7 614.2 681.2 178.7
313.6 169.5 122.7 173.8 169.5 193.1 78.0
– 2 3 4 2 3 4
30.6 10.2 10.2 1.5 3.1 12.7 3.5
16.1 17.7 19.3 20.0 20.0 17.3 19.7
2711.5 955.6 958.6 229.7 210.3 218.8 212.4
398.5 309.3 322.3 99.2 89.2 300.2 89.8
40.0 10.0 15.1 9.4 6.9 13.9 7.0
17.3 19.3 18.2 18.4 19.9 17.3 18.0
2190.9 294.9 1144.0 234.7 455.5 2482.9 634.1
262.8 145.3 235.7 178.7 101.6 291.5 161.6
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Table 5 – The average values of combustion tests Wood material (adhesive type vs. impregnation material)
O2 (%)
S.D.
Foura -layered chestnut (D-VTKA–borax) Four-layered chestnut (PVAc–borax) Four-layered white oak (D-VTKA–borax) Four-layered white oak (PVAc–borax) Four-layered chestnut (D-VTKA–zinc chloride) Four-layered chestnut (PVAc–zinc chloride) Three-layered white oak (D-VTKA–borax) Four-layered white oak (PVAc–zinc chloride) Four-layered white oak (D-VTKA–zinc chloride) Three-layered chestnut (PVAc–borax) Two-layered chestnut (PVAc–zinc chloride) Two-layered chestnut (PVAc–borax) Three-layered chestnut (PVAc–zinc chloride) Three-layered white oak (PVAc–borax) Three-layered white oak (PVAc–zinc chloride) Three-layered chestnut (D-VTKA–borax) Two-layered chestnut (D-VTKA–borax) Two-layered white oak (D-VTKA–borax) Two-layered white oak (PVAc–borax) Two-layered white oak (PVAc–zinc chloride) Three-layered white oak (D-VTKA–zinc chloride) Chestnut (D-VTKA–control) Three-layered chestnut (D-VTKA–zinc chloride) Two-layered chestnut (D-VTKA–zinc chloride) Two-layered white oak (D-VTKA–zinc chloride) White oak (PVAc–control) Chestnut (PVAc–control) White oak (D-VTKA–control)
20.4
1.1
20.2
a
HG
CO (ppm)
S.D.
HG
Ash rate (%)
S.D.
HG
Temperature (◦ C)
A
2834.7
2.2
A
18.1
2.3
H
78.7
2.2
E
1.3
A
2271.5
3.1
B
22.7
1.6
G
73.8
2.3
E
20.0
1.5
A
2132.4
3.1
B
28.1
2.5
G
99.2
2.5
E
19.9
1.2
B
2135.9
4.5
B
28.0
2.2
G
82.5
1.4
E
19.8
1.3
B
1482.9
3.2
C
40.7
1.5
E
161.6
2.3
D
19.6
1.4
B
1190.9
2.3
D
31.3
2.4
F
148.0
3.4
D
19.3
1.2
B
1188.8
3.5
D
34.2
2.2
F
122.3
1.4
D
19.1
1.4
B
1115.1
3.4
D
44.3
1.7
E
162.9
2.4
D
19.1
1.3
B
1330.0
2.3
C
40.2
2.3
E
189.8
1.5
D
19.0
1.4
B
1634.1
2.6
C
30.7
1.6
F
122.7
2.4
D
18.6
1.2
C
844.0
3.2
F
47.1
2.2
E
169.5
2.2
D
18.6 18.5
1.3 1.2
C C
894.9 844.0
4.3 3.4
F F
49.5 40.4
2.3 1.4
E E
169.5 193.1
45.3 3.6
D D
18.5
1.2
C
1033.1
4.2
D
36.0
3.2
F
124.9
5.2
D
18.4
1.4
C
983.3
3.4
E
52.8
2.4
D
205.6
3.2
C
18.2
1.3
C
1214.9
4.3
C
27.7
2.3
G
135.7
5.3
D
18.1
1.2
C
455.5
3.2
K
39.6
1.7
F
145.3
3.1
D
17.7
1.4
D
418.1
3.4
K
56.2
1.6
D
209.3
4.4
C
17.3
1.3
D
521.6
3.3
I
51.7
1.3
D
195.4
3.7
D
17.3
1.2
D
844.0
3.2
F
52.8
1.4
D
256.8
3.6
C
17.3
1.5
D
710.1
4.5
G
48.1
2.5
E
200.2
3.5
C
17.3 17.3
1.2 1.4
D D
806.7 982.9
4.2 4.4
O E
80.4 45.1
2.2 2.4
A E
262.8 201.5
4.5 3.4
C C
16.9
1.2
E
271.7
3.2
M
56.8
2.3
D
201.6
3.3
C
16.8
1.4
E
355.6
2.4
L
51.8
2.5
D
289.2
2.5
C
16.7 16.3 16.1
1.2 1.2 1.4
E E E
121.6 210.3 153.6
2.2 3.2 3.4
N P N
69.1 74.8 82.4
2.3 2.4 2.6
C B A
324.2 313.6 398.5
3.3 3.2 3.5
B B A
S.D.
HG
Number of layers.
a result of getting far away of the flame source from fire tube ¨ ¸ ifc¸i, 2005). The highest concentration of SO2 was (Uysal and Ozc observed in zinc chloride (1.43 ppm) impregnated LVL samples, the highest increase in NOx concentration was observed in white oak control samples (1.27 ppm). However, the temperature did not go up to 1000 ◦ C, so SO2 and NOx were not thoroughly observed.
4.
Discussions
There were no significant changes in pH values and densities of solutions before and after impregnation. This was due to the use of a fresh solvent for each impregnation variation. For amount of retention, zinc chloride solution had the
8
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Table 6 – Combustion ratios according to the first mass (%) Adhesive type
Impregnation material
Control Borax PVAc Zinc chloride Control Borax D-VTKA Zinc chloride
Number of layers (mm)
White oak First mass (g)
Last mass (g)
– 2 3 4 2 3 4
145.7 165.7 161.1 175.8 170.3 175.2 160.5
45.0 80.0 100.8 126.4 69.2 65.0 89.4
– 2 3 4 2 3 4
140.7 149.8 145.7 146.4 145.9 142.1 165.2
25.3 89.6 95.8 90.5 70.3 70.8 75.2
highest value; this could be due to its high-density value ¨ ¸ ifc¸i, 2001). Obtaining high retention value according to (Ozc wood type and laminated layer thickness could be because chestnut had lower density compared to white oak. Sapwood of chestnut has narrow cross-section, and trachee diameters of chestnut is wider, although yearly rings of both wood materials have large trachee (Bozkurt and Erdin, 1997). And these might have increased the retention ratio of impregnation material. At the end of combustion test, the highest weight loss was found in chestnut wood control samples, the lowest was found in four-layered laminated chestnut samples bonded with DVTKA adhesive. LVL having high number of layers might have blocked the fire. The amount of O2 did not get lower; because of that there was not any combustion. Higher amount of CO comes out if there is not full combustion. The temperature might have got a bit higher because of anatomical structure of white oak wood having extractive materials. The highest amount of unburnt piece and ash ratio was found amongst white oak wood control samples, and the lowest in fourlayered laminated chestnut samples treated with borax and bonded with D-VTKA adhesive. It was reported in the literature that the temperature must be increased up to 275 ◦ C for the wood burning itself. So, it is necessary for wood material to be impregnated with chemical materials in order to increase the resistance of wood against fire (Le Van and Winandy, 1990). In another study; it was determined that boric acid, ammonium phosphate and borax, ammonium sulfate and chloride, zinc chloride and borate, phosphoric acid, dicyanodiamide sodium borate were commonly used materials to protect wood and composite materials from fire (Maloney, 1977).
5.
Conclusions
As a result, borax was found to be an effective fire-retardant chemical in LVL produced from chestnut bonded with PVAc adhesive. In other words, borax reduces combustion of LVL. It
Chestnut
Amount of combustion (%)
First mass (g)
Last mass (g)
Amount of combustion (%)
69.11 51.71 36.05 28.01 59.34 52.89 44.38
103.0 121.3 116.4 110.1 115.7 118.7 130.0
25.9 61.2 80.6 85.1 61.2 70.7 89.2
74.85 49.54 30.75 22.70 47.10 40.43 31.38
82.46 56.20 34.20 28.15 51.81 48.17 40.20
97.5 110.9 104.6 110.8 103.4 100.9 104.2
19.1 66.9 75.6 90.7 65.3 75. 61.7
80.41 39.67 27.72 18.14 56.84 45.17 40.78
can be said that the usage life of the material can get longer if they are bonded with PVAc adhesive. LVL produced from chestnut wood should especially be impregnated with borax or zinc chloride in case it is exposed to fire. This decreases the usage of forest sources and supports the national economy.
Acknowledgement This study was made as MSc Thesis by Oktay OKC ¸ U in the Graduate School of Natural and Applied Sciences, Zonguldak Karaelmas University, Zonguldak 2006 (in Turkish).
references
Anon., 1974. TS 345, Operation Methods for the Effect of Wood Impregnation Materials. Turkish Standard Institute. Anon., 1976. TS 2472, Unit Volume Weight for Physical and Mechanical Tests. Turkish Standard Institute, Ankara. Anon., 1988. TS 5724, Wood Protection—Determination of Boron, Copper, Chrome and Arsenic Quantities in Impregnated Wood and Impregnation Materials Solving in Water-Volumetric Method. Turkish Standard Institute. Anon., 1999. TS En 386, Bonded Laminated Wood—Performance and Military Production Conditions. Turkish Standard Institute. Anon., 1999. Producer Firm Text, Polisan Dilovası-Gebze. Instruction Manuel. Kocaeli, Turkey. Anon., 2007. ASTM-D 1413-07, Standard test method for wood preservatives by laboratory soil-block culture. Annual Book of ASTM Standards. ASTM Standards, West Conshohocken, PA, USA. Anon., 2007. ASTM E 69-02, Standard Test Method for Combustible Properties of Treated Wood by the Fire-Tube Apparatus. ASTM Standards, USA. Bozkurt, Y., Erdin, N., 1997. Wood Technology, Istanbul University. Forest Faculty Publication, Turkey, pp. 237–345. Eckelman, C.A., 1993. Potential uses of laminated veneer lumber in furniture. Forest Product J. 43, 19–24. Kozlowski, R., Helwig, M., Przepiera, A., 1995. Light-weight, environmentally friendly, fire retardant composite, board for
j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 1 9 9 ( 2 0 0 8 ) 1–9
panelling and construction. Inorg. Bonded Wood Fiber Compos. Mater., 6–11. Le Van, S.L., Winandy, J.E., 1990. Effects of fire retardant treatments on wood strength: a review. Wood Fiber Sci. 22, 13–131. Maloney, T.M., 1977. Modern Particleboard and Dry-Process Fiberboard Manufacturing. Miller Greeman Publishes, Sanfrancisco, pp. 13–15. ¨ ¸ ifc¸i, A., 2001. Technological characteristics of impregnated Ozc laminated wood materials. PhD Thesis. G.U. Institute of Science, Ankara. ¨ ¸ ifc¸i, A., 2004. Combustion properties of laminated veneer Ozc lumber of Calabrian pine after impregnating. Teknoloji 7 (1–2), 1–11.
9
Stevens, W.C., Turner, N., 1974. Wood Bending Handbook, UK, pp. 90–94. ¨ ¸ ifc¸i, A., 2000. Combustion properties of laminated Uysal, B., Ozc wood material produced with PVAc adhesive from lime wood (Morus alba L.). J. Gazi Univ. Sci. Inst. 13 (4), 1023–1035. ¨ ¸ ifc¸i, A., 2005. Combustion properties of laminated Uysal, B., Ozc veneer lumbers bonded with polyvinyl acetate and phenol formaldehyde adhesives and impregnated with some chemicals. Combust. Sci. Tech. 177, 1253–1271. White, R.H., 1988. Analytical methods for determining for resistance timber members the SFPE. Hand Book of Fire Protection Engineering, vol. 8. Wood Sci. and Tech, pp.133–142. Williams, L.H., Mauldin, J.K., 1986. Integrated protection against lyctid beetloe infectations. Forest Product J. 36, 11–28.