CC BY
34
DOI 10.18551/rjoas.2019-07.40
COMPARISON OF DENSIFIED SENGON AND MAHANG BOARDS AT 43% DENSIFICATION TARGET, 150°C TEMPERATURE, AND 6.0 MINUTE PRESSING TIME
Iskandar*
Politeknik Pertanian Negeri Samarinda, Indonesia
Budiarso Edy, Wardhani Isnayuniar, Sulistyobudi Agus
University of Mulawarman, Samarinda, Indonesia
*E-mail: [email protected]
ABSTRACT
This research used sengon and mahang wood. Sengon was taken as a representative of plantations and Mahang was taken as representative of natural forests. Sengon and Mahang possess low density, therefore it requires strength improvement. One of the methods used is densification. The study used the parameters of the previous research which were considered optimal. This research used 3.5 cm initial thickness, 6 minutes densification time, 150oC temperature, and initial treatment by boiling for 45 minutes. Research result exhibited an increased density in sengon and mahang's radial and tangential plane with a percentage of 50%. The Dunnet test results on radial plane parallel press and perpendicular press, as well as on tangential plane parallel press and perpendicular press, exhibited a significant hardness increase compared to the control board. Furthermore, the compressive strength parallel to sengon and mahang densified board fiber is higher compared tocontrol board fiber.Sengon board displayed an increase of 73.75% on the radial board plane and 97.58% on the tangential board plane. Mahang board displayed a lower increase of 39.05% on the radial board plane and 43.00% on the tangential board plane.
KEY WORDS
Densification, density, hardness, compressive strength parallel, fiber.
The diminishing supply of commercial wood species as building materials and furniture encouragedthe community to replace it with other types of wood, especially woods possessing low density. However, these type of wood is limited in number and yield. Therefore, it is necessary to find a solution that can overcome the problem of scarcity of wood, for example by increasing the density of certain types of wood. Increasing the wood densitycould be conducted by filling wood cells with fillers and pressing method. This research aimed to increase Sengon and Mahang wood density, considering that both types are fast growing. Sengon was taken as a representative of plantations and Mahang was taken as a representative of natural forests. Fast-growing wood is an alternative to replace the function of the wide-leaf plant as flooring, interior, molding, and furniture (Inoue, 1996) and for structural construction wood applications (Tomme at al, 1998). Solid wood densification was first carried out in Germany in the early 1930s under the name Lignostone (Kollmann et al, 1975). In the United States, wood densification products are known as Staypak (US Forest Products Laboratory, 1999), which are in the form of wood products densification with heat treatment. USDA (1999) in Wardhani (2005) explained that densification enhances wood strength properties such as flexural (MOE, MOR and stress at proportional limits), compressive strength, tensile strength, shear strength, density and hardness at an average greater than 150%. According to Iida and Norimoto, 1987, the quality of densification such as dimensional stability, uniformity, increased strength and smoothness of the surface is only temporary.The influence of temperature and moisture content of the densified wood will recover close to its original form. Therefore technology is needed to maintain permanent densification results.
METHODS OF RESEARCH
The wood mechanical properties assessment used Universal Testing Machine (UTM). The physical properties test used oven and weighing method. The results were calculated using water content and density formula.
Wood Sample Preparation Research Procedure. The sengon tree used was about 80 cm in diameter. Mahang tree used was40 cm in diameter. The sample was taken in a straight section in the middle of the trunk. Afterward, 4 cm thick and 2-meter length board were produced. The wood sample used required the radial and tangential plane. The sample board was left in the open air for three months duration. The sample board was cut into a 40 m x 40 cm x 2.0 cm control board, and one 40 cm x 40 cm x 3.5 cm board. Before the process of densification, the boards were air-driedto reach a moisture content of 12-18%for approximately 6 weeks.
Densification Process. The sample board was boiled for 45 minutes at a temperature of 100 oC (wood inserted after boiling water). After the boiling process, the board was directly wrapped with aluminum foil and put into the press machine. Pressing was conducted after the temperature reaches 150 oC. The pressing was conducted for 6 minutes, i.e after the wood reached a thickness of 2 cm, the press machine was left for 6 minutes. Afterward, the press machine was turned off and opened after 24 hours. After the densification process, the board is air-dried for approximately 6 weeks until the water content reaches 12-18%.
Test Sample Production Process. Wood samples from the densification process werre made into the physical and mechanical properties test sample. The test sample was produced according to a predetermined size. The physical properties measured were density. The mechanical properties assessed were wood hardness and compressive strength parallel to fiber. The sample size for assessing physical properties referred to the standard JIS Z 2102 (1957) and JIS Z 2103 (1957). The sample size for assessing mechanical properties referred to the standard JIS Z 2113 (1963).
2 cm
2 cm
Description
□
2 cm
Sample of Compressive Strength Parallel to Fiber (2 x 2 x 6) cm Sample of Wood Hardness (2 x 2 x 6) cm Sample of Wood Density (2 x 2 x 2) cm
Figure 1 - Sample Respective Position on Densified Board
Data Analysis. The hardness analysis used a completely randomized design, utilizing factorial experiments with 2 treatment factors, namely factor A wood position (radial and tangential plane), and factor B compression position (parallel to the press and perpendicular to the press). Five repetitions were made on each sample.
RESULTS AND DISCUSSION
Dry air density and dry kiln density in the radial and tangential plane were recorded to determine density difference.
Table 1 - Shrinkage comparison on densified board and control board
Wood type Wood Position Dry air density (gr/cm3) Dry kiln density (gr/cm3) Shrinkage (%)
Radial 0.6245 0.6070 2.81
Sengon Tangential 0.5926 0.5815 1.87
Control 0.4008 0.3732 6.88
Radial 0.4650 0.4582 1.47
Mahang Tangential 0.4625 0.4560 1.41
Control 0.3056 0.2613 14.50
The dry air density in the sengon wood radial plane is 0.6245 gr / cm3. After kiln drying process, it reduced to 0.6070 gr / cm3 or shrinks by 2.81%. Sengon tangential planedry air density value is 0.5926 gr /cm3. After kiln drying process, it reduced to 0.5815 gr / cm3 or shrinks by 1.87%. The dry air density value of the sengon control board was 0.4008 gr / cm3. After kiln drying process, it reduced to 0.3732 gr / cm3 or shrank by 6.88%. The dry air density of the mahang wood radial plane is 0.4650 gr / cm3.After kiln drying process, it reduced to 0.4582 gr / cm3 or shrinks by 1.47%. The tangential planedry air density value is 0.4625 gr / cm3. After kiln drying process, it reduced to 0.4560 gr / cm3 or shrinks by 1.41%. The dry air density value of mahang control board is 0.3056 gr / cm3.After kiln drying process, it reduced to 0.2613 gr / cm3 or shrinks by 14.50%. The sengon control board shrinks 3 times compared to the densified board. Mahang control board shrinks 9.5 times compared to each densified board. Therefore densification process is capable to reduce wood shrinkage, hence allowing overcoming dimensional stability thickness.
0,7000 0,6000 0,5000 0,4000 0,3000 0,2000 0,1000 0,0000
Radial Tangential Control Radial Tangential Control Sennnn Mahang
¡^ Dry Air Density (gr/cm3)
s Dry Kiln Density (gr/cm3)
Figure 2 - Sengon and Mahang Density on Radial and Tangential Plane
Figure 2 exhibited the density difference between the radial and tangential plane.Densified sengon board density is 0.60 and densified mahang board density is 0.45. The control density is 0.40 and 0.30 on sengon and mahang respectively. The magnitude of the densified board density is strongly influenced by the control density or initial density.
Table 2 - Increased Sengon and Mahang DensityCompared to Control Board
Wood type Wood Position Control (gr/cm3) Density Dry Air Density (gr/cm3) Dry Kiln Density (gr/cm3) Density Increase Compared to Control (%)
Dry Air Dry Kiln
Sengon Mahang Radial 0.4008 0.6245 0.6070 55.83 51.45
Tangensial Radial 0.4008 0.3056 0.5926 0.4650 0.5815 0.4582 47.87 52.15 45.10 49.92
Tangensial 0.3056 0.4625 0.4560 51.33 49.20
Table 2 exhibited both wood typedry air density and dry kiln density increased by 50% compared to control density.Therefore the densification process is capable to increase wood density. Dodi Nandika (2014) increased sengon density utilizing compregnation process up to 80 (70%). Sulistyono (2001) conducted a 50% target densification on agathis had succeeded in increasing its density. Agathis density increased by 74% on the tangential plane and 72% on the radial plane compared to control. Murhofiq's (2000) study exhibited
that agathis wood densification up to 50% of its original thickness was able to increase its density from 0.41 g/cm3 to 0.9 g/cm3. Sengon wood, with a density of 0.23 g/cm3,exhibited density increase to 0.48 g/cm3 after solidification.
Sengon and Mahang densified board density is 50% higher than the control. The density percentage would increase when the densificationtarget is increased from 43% to 50%. This research reduced the initial thickness from 3.5 cm to 2 cm. Therefore, the densification target is around 43% due to potential damage to the board. A high percentage target would risk damage, especially the treatment in the form of pre-press heating by boiling in a temperature of 100 oC.Other research, however, usedautoclave. Therefore allowing control over heat and pressure.
Sengon and Mahang Hardness. Based on the analysis of diversity on densified sengon board hardness, as presented in the following table 3, exhibited treatment or factor A (radial and tangential plane) have a significant influence on increasing densified board hardness. On the other hand, factor B (parallel and perpendicular pressure), as well as A and B factors interaction do not significantly influence densified board hardness. The analysis of diversity on densified mahang board hardness, as presented in table 4, exhibited there is no source of diversity values significantly different as all F count <F table. The following analysis used the dunnet test to ascertain whether there is a significant difference or not.
Table 3 - Anova on densified sengon board
Source of Diversity JK db KT F hit F- table 5% 1%
P 66,141.40 3 22047.13 11.14 3,24 5,29
A 48,609.80 1 48609.80 24.57 4,49 8,53
B 16,017.80 1 16017.80 8.10 4,49 8,53
A*B 1,513.80 1 1513.80 0.77 4,49 8,53
G 31,654.80 16 1978.42
Total 163,937.60 19
Table 4 - Anova on densified mahang board
Source of Diversity JK db KT F hit F- table
5% 1%
P 3,290.95 3 1096.98 0.99 2.21 3.04
A 432.45 1 432.45 0.39 3.26 5.25
B 2,856.05 1 2856.05 2.58 3.26 5.25
A*B 2.45 1 2.45 0.00 2.63 3.89
G 17,703.60 16 1106.48
Total 24,285.50 19
Table 5 - Sengon hardness increase compared to control
Board type Test Position Control Hardness Increase (%)
Radial Parallel Press 122.00 325.00 166.39
Perpendicular Press 122.00 285.80 134.26
Tangential Parallel Press 195.00 441.00 126.15
Perpendicular Press 195.00 367.00 88.21
500,00 450,00 400,00 350,00 300,00 250,00 200,00 150,00 100,00 50,00 0,00
Parallel Press Perpendicular Parallel Press Perpendicular Press Press
" Control — Hardness
Radial Tangential
Figure 3 - Sengon hardness increase compared to control
Table 6 - Mahang hardness increase compared to control
Board Type Test Position Control Hardness increase (%)
Radial Parallel Press 88.20 158.40 79.59
Perpendicular Press 88.20 183.00 107.48
Tangential Parallel Press 113.40 168.40 48.50
Perpendicular Press 113.40 191.60 68.96
250,00
200,00
150,00
100,00
50,00
0,00
Parallel Press
Perpendicular Parallel Press Press
Perpendicular Press
Radial
Tangential
" Control e Hardness
Figure 4 - Mahang Hardness Increase Compared to control Table 7 - Densified Sengon Board Hardness Dunnet Test Result
Wood Plane & Test Position |j1 (Hardness) ji2 (Control) ||2 - |1| DLSD
Radial Parallel press 325.00 158.80 166.2 * 72.86
Radial Perpendicular press 285.00 158.80 126.2 * 72.86
TangentParallel press 441.00 158.80 282.2 * 72.86
Tangential Perpendicular press 367.00 158.80 208.2 * 72.86
Table 8 - Densified Mahang Board Hardness Dunnet Test Result
Wood Plane & Test Position ji1 (Hardness) ji2 (Control) ||2 - |1| DLSD
Radial Parallel press 158.40 100.80 57.6 * 54.49
Radial Perpendicular press 183.00 100.80 82.2 * 54.49
Tangent Parallel press 168.40 100.80 67.6 * 54.49
Tangential Perpendicular press 191.60 100.80 90.8 * 54.49
Based on Dunnet Test result, densified board density to the control value were greater than the DLSD value, indicating that there was an increase in sengon hardness and significantly higher levels of control. Figures 3 and 4 exhibits sengon and mahang radial plane hardness are smaller compared to the tangential plane. There is a difference between sengon and mahang hardness based on pressing direction. Sengon parallel press hardness is higher than parallel press. On the other hand, mahang parallel press hardness is lower compared to perpendicular press. This occurred due to different cell structures in each type. The densified wood cells were observed using an Electronic Microscope (SEM) Scan.
Increased sengon and mahang densified boards hardness are presented in tables 5 and 6. The tables exhibited that the increase in sengon hardness ranges from 88.21% to 166.39%, and the increase in mahang hardness ranges from 48.50% - 107.48%. Murhofiq (2000) stated that wood densification up to 50% was able to increase the hardness value of sengon and agathis tangentialplaneby 376% and 229% respectively.
Factors influencing the value of wood hardness are density, wood tenacity, wood fiber size, binding capacity between wood fibers and wood fiber composition (Mardikanto et al. 2011). The hardness increase found in this study was lower or only about half of Murhofik's
results. This was influenced by two things. The initial treatment was boiling at a temperature of 100 oC. On the other hand, the comparative study used an autoclave where the temperature and pressure could be freely controlled. This study used 43% target, while the comparative study used a target of 50%.
Compressive Strength Parallel to Sengon and Mahang Fiber. Compressive strength parallel to the fiber is useful if densified wood is used as poles for table legs, chair legs, cupboard frames, etc.
Table 9 - Compressive Strength Parallel to Sengon and Mahang Fiber Data
Board Type
Sengon
Compressive Strength Parallel to Fiber
Mahang
Radial Tangential Control
464.96 528.73 267.60
363.69 374.02 261.56
600,00
500,00
400,00
300,00
200,00
100,00
0,00
-JKTSS Sgn - KTSS Mhg
Radial
Tangential
Control
Description: KTSS = Compressive Strength Parallel to Fiber Figure 5 - Compressive Strength Parallel to Fiber in Radial and Tangential Plane
The figure exhibited that compressive strength to sengon and mahang fiber is similar to the control board. However, compressive strength to sengon fiber value is more than mahang compressive strength to fiber value after pressing process. Each wood type responded differently to the densification process. The differences were caused by respective wood cell composition.
The increase of compressive strength to fiber after the densification process is presented in table 10. It exhibited that compressive strength to sengon and mahang fiber increased on the tangential plane. The compressive strength to sengon fiber is 528.72 kg/cm2on a tangential plane and 464.96 kg/cm2on the radial plane. The compressive strength to mahang fiber is 374.02 kg/cm2on a tangential plane and 363.69 kg/cm2on the radial plane. Furthermore, the compressive strength parallel to sengon fiber increase is 100% compared to control. On the other hand, the compressive strength parallel to mahang fiber increase is less than 45%. Similar to Sulistyono's research (2001), it stated that agathis compressive strength experienced 100% compared to control, about 532.74 kg/cm2 to 683.68 kg/cm2compared to initial strength (control) at 360.11 kg/cm2 to 367.15 kg/cm2. Rakhma Hidayat (2012) stated that compressive strength parallel to jabon wood increased by 21% compared to control.
According to Seng (1951), compressive strength value between 300 - 425 km/cm2is classified as Strength III class, 425 - 650 kg/cm2is classified as Strength II class, and >650 kg/cm2 is classified as Strength I class. Densified sengon board is classified as Strength II class and densified mahang board is classified as Strength III class.
Table 10 - Compressive Strength Parallel to Sengon and Mahang Fiber Increase
Wood Type Board Type Control (kg/cm2) Compressive Strength Parallel to Fiber(kg/cm2) Increase (%)
Sengon Radial 464.96 73.75
Tangential 528.73 97.58
Mahang Radial 363.69 39.05
Tangential 374.02 43.00
600,00
500,00
400,00
300,00
200,00
100,00
0,00
Control KTSS
Radial Tangential
Sengon
Radial Tangential
Mahang
Figure 6 - Compressive Strength Parallel to Fiber Increase on Radial and Tangential Plane
The histogram exhibited that compressive strength parallel to sengon and mahang fiber is similar to control (grey histogram). The average compressive strength parallel to sengon fiber is higher compared to mahang. The compressive strength to sengon and the mahang tangential plane is higher compared to the radial plane.
CONCLUSION
Sengon and Mahang densified board density is 50% higher compared to control. Sengon board hardness increases about 88.21-166.39%. On the other hand, Mahang board hardness increases about 48.50-107.48%. Compressive strength parallel to sengon and mahang fiber increases occurred on the tangential plane. Compressive strength parallel to sengon fiber is 528.72 kg/cm on tangential plane and 464.96 kg/cm2 on radial plane. Furthermore, compressive strength parallel to mahang fiber is 374.02 kg/cm2 on the tangential plane and 363.69 kg/cm2 on the radial plane.
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