Eur. J. Wood Prod. (2013) 71:583–589 DOI 10.1007/s00107-013-0712-5
ORIGINALS ORIGINALARBEITEN
Influence of processing parameters on some properties of oil palm trunk binderless particleboard Jia Geng Boon • Rokiah Hashim • Othman Sulaiman Salim Hiziroglu • Tomoko Sugimoto • Masatoshi Sato
•
Received: 12 September 2012 / Published online: 12 June 2013 Ó Springer-Verlag Berlin Heidelberg 2013
Abstract The objective of the study was to evaluate some properties of experimental binderless particleboards produced from various processing parameters. Three different temperatures (160, 180, 200 °C), two different hot pressing times (15, 20 min) and two different pressures (5, 10 MPa) were applied in manufacturing the binderless particleboard. Three replications of each of the 12 different types of boards with a target density of 0.60 g cm-3 were produced. The thickness swelling, dimensional changes associated with changes in relative humidity, bending strength, internal bonding strength, and soil burial decay test were evaluated. Increase of temperature, duration of hot pressing and pressure increased the properties of specimens. Thickness swelling nearly met the requirement of European Standard for use in humid condition. Some of the specimens showed promising mechanical properties and met the requirement of European Standard.
J. G. Boon R. Hashim (&) O. Sulaiman Division of Bioresource, Paper and Coatings Technology, School of Industrial Technology, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia e-mail:
[email protected] S. Hiziroglu Department of Natural Resource, Ecology and Management, 303G Agricultural Hall, Oklahoma State University, Stillwater, OK 74078-6013, USA T. Sugimoto Japan International Research Center for Agricultural Sciences, 1-1, Owashi, Tsukuba, Ibaraki 305-8686, Japan M. Sato Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1, Yayoi, Bunkyo-ku, Tokyo 113.8657, Japan
Einfluss von Prozessparametern auf verschiedene Eigenschaften bindemittelfreier Spanplatten aus ¨ lpalmenholz O Zusammenfassung Ziel dieser Studie war es, ausgewa¨hlte Eigenschaften von unterschiedlich hergestellten bindemittelfreien Laborspanplatten zu bestimmen. Die Spanplatten wurden mit drei verschiedenen Temperaturen (160, 180, 200 °C), zwei Heißpresszeiten (15, 20 min) und zwei verschiedenen Pressdru¨cken (5, 10 MPa) jeweils mit einer Solldichte von 0,60 g/cm3 hergestellt. Von jedem der zwo¨lf verschiedenen Typen wurden drei Platten hergestellt. Es wurden die Dickenquellung, die Maßa¨nderungen in ¨ nderungen der relativen Luftfeuchte, die Verbindung mit A Biegefestigkeit sowie die Querzugfestigkeit untersucht und Freilandversuche im Erdkontakt durchgefu¨hrt. Eine ho¨here Temperatur, la¨ngere Heißpressdauer und gro¨ßerer Druck ergaben bessere Eigenschaften der Pru¨fko¨rper. Die Dickenquellung erfu¨llte fast die Anforderung der europa¨ischen Norm fu¨r eine Außenanwendung unter feuchten Bedingungen. Einige der Pru¨fko¨rper wiesen vielversprechende mechanische Eigenschaften auf und erfu¨llten die Anforderungen der europa¨ischen Norm.
1 Introduction Wood composite panel applications are widely found in many industries including furniture and packaging. The worldwide demand for wood composite panels is still growing (Gamage et al. 2009). The combinations of wood either in form of strands, chips or other geometry dimension, together with synthetic adhesives provide wood composite panels with good performance. However, these synthetic adhesives have concomitantly some negative
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impact on environmental and health issues. One of the common adhesives used in particleboard manufacturing are formaldehyde based adhesives. The formaldehyde emission has been proved to be carcinogenic (Que et al. 2007). Besides, the disposal of synthetic adhesive composite panels has led to landfill issue due to the slow degradation rate of synthetics adhesives. To overcome the issue of synthetic resins, many researches have been carried out and study of binderless composite panel as one of these efforts. Binderless composite panels could be an alternative for reducing the usage of synthetic adhesive composite panels. The basis of binderless composite panels is to bond the biomass material together without using synthetic adhesives (Angle`s et al. 2001). Self-bonding can be achieved by reaction of chemical constituents contained in the biomass consolidated with heat and pressure. Together with biomass species of raw material, these aspects could influence the performances of the binderless composite panel (Hashim et al. 2011a). Hence, processing parameters such as pressing temperature, pressing duration and pressure, are important for the binderless composite panel production. Some studies point out that lignin, some carbohydrate substances such as sugar and starch have been suggested as the potential chemical constituents contributing to bonding of binderless composite panels (Angle`s et al. 2001; Hashim et al. 2011a). Lignin is well known as natural compound commonly located in between the cell wall and providing the cohesion function to the cell wall (Chabannes et al. 2001). Together with carbohydrate compounds including sugar and starch, these compounds are important for the bonding system of binderless particleboards (Wi et al. 2005). The conjunction of these chemical constituents with hot pressing temperature and duration allow these chemical constituents to thermally react. Lee et al. (2011) found that the minimum thermal decomposition rates for major sugar including sucrose, glucose, and fructose were at 138, 150 and 107 °C, respectively. Sun and Tomkinson (2001) indicated glass transition point of oil palm trunk lignin obtained from potassium based pulping was around 120 °C. Combined with pressure during hot press will allow good contact of particles and improvement of the inter-bonding between the particles. Some aspects of binderless panels were studied. Halvarsson et al. (2009) studied the chemical treatment for binderless fiberboard from wheat straw. Angle`s et al. (2001) investigated the effect of pretreatment and lignin addition to binderless board produced from spruce and pine. Hashim et al. (2010, 2011a, b) researched characteristics of different biomass components from oil palm biomass in producing binderless particleboard, the effect of particle geometry of oil palm trunk on binderless particleboard, and the effect of pressing temperature on
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binderless particleboard made from fine raw materials. van Dam et al. (2004) reported on production process of coconut husk binderless board. However, to our best knowledge of literature reviews, research on the effect of processing parameters on oil palm trunk binderless particleboard using rough particles has still not been reported. Therefore, the aim of this study was to investigate the influence of combination of processing parameters such as temperature, pressure and pressing time on some properties of oil palm trunk binderless particleboard.
2 Materials and methods 2.1 Materials Oil palm trunk samples were obtained from FELCRA Kampung Gajah Perak Malaysia. Oil palm trunks were chipped into coarse particles using hammer mill and ground with a grinder passing a mesh of 2 mm opening size no. 10. The moisture content of the particles was approximately 10 %. 2.2 Chemical composition analysis Oil palm trunk samples were ground to pass through a sieve of mesh size no. 40. The composition of extractives, cellulose, hemicelluloses and lignin were determined based on the methods used by Hashim et al. (2011a). Sample preparation for analysis was performed according to TAPPI T 264 cm-97 (1997). Extractives composition was determined according to TAPPI T 204 cm-97 (1997). Holocellulose composition was determined using a method by Wise et al. (1946). Cellulose composition was measured by dissolving hemicelluloses with 17.5 % sodium hydroxide. Hemicelluloses composition was determined by weight reduction of cellulose composition from holocellulose. Lignin composition was measured according to TAPPI T 222 om-22 (2002). Starch was extracted and the yield was determined according to a method performed by H’ng et al. (2011). Samples were steeped in 0.2 % sodium metabisulfite solution at room temperature for 72 h. The slurry was filtered and the residue was washed with distilled water. The residue was then centrifuged to separate starch–protein mixture. The starch content of the sediment was measured using UV spectrophotometer at wavelength 650 nm. The sugar extraction was performed according to Abreu et al. (2001). The samples were extracted with ethanol and the solvent was removed via rotary evaporator. The brown yield was defatted with diethyl ether and sugar was obtained via rotary evaporator. The yield of purified sugar was then determined.
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2.3 Preparation of binderless particleboard
3.2 Physical properties
Single rum laboratory Molding Test Press (Model Fabricate GT-7014-A30) was used in producing the specimens. Laboratory hand layout particleboards with a target thickness of 0.5 cm and target density of 0.60 g cm-3 were made at different temperatures (160, 180 and 200 °C) with hot pressing times (15 and 20 min) and pressures (5 and 10 MPa, according to readings at GT-7014-A300 pressure gauge) without spacing strips. The platen was manually closed in slow speed at the beginning of hot pressing until the desired pressure was reached in order to reduce excessive expansion of mat size due to the pushing force from platen which potentially reduced the density of the board. Each combination of these parameters was carried out in triplicates. All particleboards were cut into size of 20 9 20 cm and conditioned at 20 ± 2 °C and 65 ± 5 % relative humidity prior to further evaluation.
The moisture content of specimens was in the range of 6.9–9.3 %. The thickness and density of specimens are shown in Table 1. The mean density of specimens was in the range of 0.62 –0.65 g cm-3. Generally, the specimens that were hot pressed at 10 MPa had lower thickness compared to specimens hot pressed at 5 MPa right after being removed from the hot press machine (before conditioning). However, the thickness of boards before conditioning is not presented in this paper as it was not possible to precisely measure the thickness of boards before conditioning. During the attempts of thickness measuring, the reading from caliper kept increasing. The authors believe that the spring back process begins before being able to measure the thickness of boards. The thickness of specimens after conditioning was in the range of 0.45–0.54 cm. The authors believed that the increment of the thickness was in accordance with the performance of the specimens, respectively. Fig. 1 shows an exterior view of some of the experimentally produced binderless particleboards. The specimens A, B, C were hot pressed for 20 min at 10 MPa pressure and temperatures of 160, 180 and 200 °C, respectively. As the temperature increased, the exterior of the particleboard became darker. However the effect of increasing the pressure and duration on the exterior was not obvious compared to the effect of temperature. Tables 2, 3, 4 show the dimensional and mass changes associated with the changes in relative humidity, and thickness swelling properties of specimens. Overall, the stability of the specimens against moisture was improved as the hot press temperature, hot press time, and pressure were increased. The specimens pressed at different
2.4 Testing and evaluation Moisture content (EN322 1993), density (EN 323 1993), thickness swelling (EN 317 1993), dimensional changes associated with changes in relative humidity (EN 318 2002), bending test (EN 310 1993), internal bonding strength (EN 319 1993) of samples were tested according to European Standards, respectively. Soil burial decay test (BS 1982-2, 1990) was performed according to British Standard. 2.5 Statistical analysis Tukey HSD test was employed to evaluate the comparison of the means of stability test against moisture, mechanical strength test and soil burial decay test. All results were expressed as mean ± SD.
Table 1 Thickness and density of binderless particleboard after conditioning Tab. 1 Dicke und Dichte der bindemittelfreien Spanplatten nach Konditionierung
3 Results and discussions
Processing parameter [temperature (°C), time (min), pressure (MPa)] 160, 15, 5
0.54 ± 0.02
0.62 ± 0.01
3.1 Chemical composition
160, 15. 10
0.53 ± 0.06
0.64 ± 0.01
The chemical composition analysis of oil palm trunk samples obtained in this study showed that the samples consisted of 13.97 % of extractives, 41.39 % of alpha cellulose, 23.59 % of hemicelluloses, 18.69 % of lignin, 9.44 % of sugar and 10.23 % of starch, which are in agreement with previous findings (Hashim et al. 2011a). High content of lignin, starch and sugar have been suggested as important constituents to binderless panel. The results indicated that oil palm trunk is ideal and suitable for binderless particleboard making.
Thickness (cm)
Density (g/cm3)
160, 20. 5
0.54 ± 0.03
0.62 ± 0.01
160, 20, 10
0.52 ± 0.01
0.62 ± 0.01
180, 15, 5
0.51 ± 0.08
0.62 ± 0.02
180, 15, 10
0.49 ± 0.04
0.63 ± 0.02
180, 20, 5
0.49 ± 0.04
0.62 ± 0.01
180, 20, 10
0.48 ± 0.02
0.64 ± 0.01
200, 15, 5
0.48 ± 0.01
0.62 ± 0.01
200, 15, 10 200, 20, 5
0.46 ± 0.02 0.47 ± 0.01
0.63 ± 0.02 0.64 ± 0.02
200, 20, 10
0.45 ± 0.01
0.62 ± 0.01
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Fig. 1 Exterior view of experimental binderless particleboard hot pressed for 20 min at 10 MPa and a 160 °C, b 180 °C and c 200 °C Abb. 1 Ansicht der bindemittelfreien Laborspanplatten, die u¨ber eine Dauer von 20 min und einem Druck von 10 MPa bei a 160 °C, b 180 °C und c 200 °C hergestellt wurden
Table 2 Dimensional and mass changes of binderless particleboard with changes in relative humidity from 65 to 85 % Tab. 2 Maß- und Massea¨nderungen der bindemittelfreien Spanplat¨ nderung der relativen Luftfeuchte von 65 auf 85 % ten bei einer A
Table 3 Dimensional and mass changes of binderless particleboard with changes in relative humidity from 65 to 35 % Tab. 3 Maß- und Massea¨nderungen der bindemittelfreien Spanplatten ¨ nderung der relativen Luftfeuchte von 65 auf 35 % bei einer A
Processing parameter [temperature (°C), time (min), pressure (MPa)]
Processing parameter [temperature (°C), time (min), pressure (MPa)]
Changes (%) Length
Thickness
Weight
160, 15, 5
-0.92 ± 0.04a
-1.38 ± 0.05a
-1.55 ± 0.04a
160, 15, 10
-0.89 ± 0.02ab
-1.22 ± 0.05b
-1.49 ± 0.02a
160, 20, 5
-0.86 ± 0.02b
-1.13 ± 0.04c
-1.41 ± 0.02b
160, 20, 10
-0.81 ± 0.02c
-0.98 ± 0.05d
-1.35 ± 0.03b
180, 15, 5 180, 15, 10
-0.30 ± 0.02d -0.28 ± 0.00de
-0.51 ± 0.03e -0.46 ± 0.02ef
-1.23 ± 0.03c -1.19 ± 0.01cd
180, 20, 5
-0.24 ± 0.00ef
-0.41 ± 0.01f
-1.15 ± 0.02de
180, 20, 10
-0.21 ± 0.02f
-0.34 ± 0.03g
-1.12 ± 0.03e
200, 15, 5
-0.13 ± 0.02g
-0.29 ± 0.03gh
-1.01 ± 0.02f
200, 15, 10
-0.12 ± 0.00gh
-0.23 ± 0.03h
-1.00 ± 0.02f
200, 20, 5
-0.08 ± 0.00hi
-0.16 ± 0.01i
-0.92 ± 0.07g
200, 20, 10
-0.05 ± 0.02i
-0.13 ± 0.02i
-0.85 ± 0.04h
Changes (%) Length
Thickness
Weight
160, 15, 5
0.71 ± 0.00a
15.10 ± 0.21a
1.78 ± 0.02a
160, 15, 10
0.74 ± 0.05a
14.08 ± 0.22b
1.75 ± 0.01ab
160, 20, 5
0.69 ± 0.06ab
12.86 ± 0.42c
1.69 ± 0.02bc
160, 20, 10
0.65 ± 0.02b
11.15 ± 0.30d
1.65 ± 0.01c
180, 15, 5
0.53 ± 0.02c
6.64 ± 0.19e
1.18 ± 0.04d
180, 15, 10
0.48 ± 0.00cd
6.25 ± 0.12e
1.11 ± 0.03e
180, 20, 5
0.44 ± 0.00d
5.68 ± 0.19f
1.10 ± 0.02e
180, 20, 10
0.44 ± 0.00d
5.15 ± 0.24g
1.06 ± 0.01e
200, 15, 5
0.28 ± 0.00e
4.65 ± 0.09h
1.02 ± 0.07f
200, 15, 10
0.27 ± 0.02e
4.15 ± 0.09i
0.92 ± 0.04g
200, 20, 5
0.25 ± 0.02ef
3.49 ± 0.18j
0.81 ± 0.03h
200, 20, 10
0.20 ± 0.04f
3.07 ± 0.09j
0.73 ± 0.02i
Different letters within the same column are statistical significant difference at a = 0.05
temperatures with same pressing time and pressure showed significant differences in the means. The improvement showed that increasing pressing temperature had greater effect compared to increasing pressing time and pressure. However, in this research, a temperature above 200 °C could not be used to press the board. The board was severely burnt during the attempts. The improvement of stability against moisture showed that increasing of pressing time and pressure was not promising. The comparison of means of some specimens pressed at different pressing times with same temperature and pressure, or pressed with different pressure at same temperature and pressing time, showed insignificant difference. The improvement of the stability against moisture could be attributed to compressing effects of the panel. Specimens showing better stability also showed high internal
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Different letters within the same column are statistical significant difference at a = 0.05
bonding strength as discussed in the next section. Good contact between particles could help to reduce moisture penetration into panel and particles (Wong et al. 1999). However, none of the specimens met the thickness swelling requirement to be used in humid condition as specified in the European Standard EN 312 (2010). Therefore, the performance of the test specimens was only suitable for general purpose (type P1) or interior fitment in dry condition (type P2) particleboard. The least thickness swelling rate obtained from specimens pressed at 200 °C for 20 min with 10 MPa, was 25.41 %. The requirement of thickness swelling for non load-bearing particleboards use in humid condition (P3) stated in European Standard was \20 %. The setting of
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Table 4 Thickness swelling of binderless particleboard Tab. 4 Dickenquellung der bindemittelfreien Spanplatten Processing parameter [temperature (°C), time (min), pressure (MPa)]
Thickness swelling (%)
160, 15, 5
86.31 ± 1.42a
160, 15, 10
80.96 ± 1.28b
160, 20, 5 160, 20, 10
78.05 ± 1.09bc 77.31 ± 1.26c
Table 5 Mechanical strength properties and weight loss of soil burial decay of binderless particleboard Tab. 5 Mechanische Festigkeitseigenschaften der bindemittelfreien Spanplatten und deren Masseverlust bei Freilandversuchen im Erdkontakt Processing parameter [temperature (°C), time (min), pressure (MPa)]
Mechanical properties Internal bonding strength (N/mm2)
Modulus of Rupture (MPa)
Soil burial weight loss (%)
180, 15, 5
37.00 ± 1.89d
180, 15, 10
32.72 ± 2.63e
160, 15, 5
0.17 ± 0.02a
8.80 ± 0.20a
29.3 ± 2.6a
180, 20, 5
31.92 ± 3.63e
160, 15, 10
0.20 ± 0.01ab
9.23 ± 0.09ab
27.4 ± 1.0a
180, 20, 10
27.64 ± 0.89f
160, 20, 5
0.22 ± 0.00b
9.06 ± 0.05ab
25.0 ± 1.1b
200, 15, 5
32.77 ± 0.96g
160, 20, 10
0.24 ± 0.01bc
9.49 ± 0.16b
21.0 ± 0.8c
200, 15, 10
30.59 ± 0.93gh
180, 15, 5
0.32 ± 0.02d
10.85 ± 0.17c
17.1 ± 0.9d
200, 20, 5
29.09 ± 1.20h
180, 15, 10
0.35 ± 0.01de
11.06 ± 0.09cd
15.5 ± 1.7def
200, 20, 10
25.41 ± 0.87i
Different letters within the same column are statistical significant difference at a = 0.05
processing parameters used in this study of binderless particleboard specimens made from particles passed through 2 mm opening sieve was maximized. The attempt of improvement via further increase of hot pressing temperature, pressing time and pressure was not effective as the specimens were burnt and insignificant improvement, respectively. This suggests that in order to improve the stability of specimens against moisture other alternatives including some chemical constituents aspects need to be considered. For example, hemicelluloses could be responsible for the poor moisture repellent of binderless board (Angle`s et al. 2001). In future work, the aspect of hemicelluloses needs to be observed. This could help to improve the stability of the binderless particleboard against moisture and promote better performance. 3.3 Mechanical strength properties The results of bending strength test and internal bonding strength test are shown in Table 5. Overall, the pattern of modulus of rupture and internal bonding strength of specimens are similar to the stability properties of specimens against moisture. The specimens formed with high mechanical strength also showed high stability against moisture. The increment of mechanical strength by increasing pressing temperature was significantly greater than by increasing pressing time and pressure. The results showed that almost all the specimens pressed at 160 and 180 °C were not statistically significant in improving the internal bonding strength and bending strength if only by increase pressing time or pressure. The internal bonding strength and bending strength were increased when increasing the pressing time and pressure, although the
180, 20, 5
0.36 ± 0.01de
11.30 ± 0.08cd
16.2 ± 0.3de
180, 20, 10
0.38 ± 0.01e
11.51 ± 0.07de
16.3 ± 0.2e
200, 15, 5 200, 15, 10
0.49 ± 0.03f 0.52 ± 0.03fg
11.91 ± 0.30e 13.12 ± 0.25f
14.8 ± 0.1e 14.3 ± 0.2efg
200, 20, 5
0.55 ± 0.01g
14.89 ± 0.60g
13.7 ± 0.2fg
200, 20, 10
0.60 ± 0.03h
15.81 ± 0.46h
13.3 ± 0.3g
Different letters within the same column are statistical significant difference at a = 0.05
difference of means of many of the specimens were too weak to show significant difference. Generally, most of the specimens failed to meet the requirement specified in European Standard EN 312 (2010). However, some of the specimens pressed at 200 °C showed satisfactory results. Specimens pressed at 200 °C for 20 min with pressure 5 and 10 MPa respectively, met the internal bonding strength and bending strength requirement of type P1, P2 and P3 particleboard. Whereas for specimens pressed at 200 °C for 15 min, only specimens pressed at 10 MPa met the requirement of type P1. Compared to particleboard bonded with common synthetic resin such as urea formaldehyde resin, the experimental specimens with promising properties required high pressing temperature and longer time. In synthetic resins bonded particleboard, heat was applied to cure the resins to coat the particles, whereas, heat was applied in pressing binderless particleboard to allow the existing chemical compounds in the raw materials such as starch and lignin in the particles to react. These chemical compounds were mostly located in the pit of fiber or middle of fiber wall of plant (Chabannes et al. 2001; Mohd. Noor and Mohd 1999), thus, more time and heat are needed to penetrate into particles and promote the reaction. In addition, heat conductivity in hot pressing binderless particleboard might be limited compared to particleboard that was pressed with
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common liquid based synthetic resin, where the liquid resin assists in spreading the heat widely and rapidly. 3.4 Soil burial Soil burial decay rate after 60 days of incubation is shown in Table 5. The specimens hot pressed at 160 °C for 15 min pressing time with 5 MPa pressure showed highest weight loss with 29.3 %. While the specimens hot pressed at 200 °C for 20 min pressing time at 10 MPa pressure showed lowest weight loss, which was 13.3 %. With increasing pressing temperature, pressing time and pressure, the weight loss of the specimens was reduced. The influence given by pressing temperature is generally significantly greater than the influence given by pressing time and pressure. The specimens with poor mechanical strength and poor stability against moisture showed poor resistance to decay. The penetration of moisture from the testing area into the specimens could weaken the inter-particle bonding of specimens. Hence some small fragment of stake was detached, enlarging the surface of exposure to microorganisms, consequently, accelerating the decay of microorganisms to specimens. Therefore, good bonding strength and good stability against moisture could help to reduce the decay rate of specimens. The Tukey HSD test indicated that there was no improvement of weight loss when increasing the temperature from 180 to 200 °C or the pressure from 5 to 10 MPa. However the mechanical strength did increase, respectively as being discussed earlier. This could be due to the effect of mechanical strength, and resistance of the specimen against the microorganisms decay had already optimized. Furthermore, other than mechanical strength and stability against moisture, the decay could be ascribed to other reasons, such as the rich carbohydrate substance and low antimicrobial activities of oil palm itself (Loh et al. 2011). The effect of processing parameters on the resistance of specimens to soil burial decays were limited to a certain extend.
4 Conclusion The effects of processing parameters including pressing temperature, pressing time, and pressure on binderless particleboard properties were studied. This study indicated that increasing of pressing temperature, pressing time, and pressure, increased the stability against moisture, mechanical strength and the resistance of microorganisms decays of the specimens. The effect given by increasing the pressing temperature was significantly greater than by increasing pressing time and pressure. The specimens pressed at 200 °C and 10 MPa for 20 min showed the best
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results in stability tests against moisture, mechanical strength tests, and soil burial decay tests. However, the stability of specimens against moisture showed that the specimens are not suitable for use in humid conditions. In future, further work will be conducted to improve the performance of binderless particleboard to better values and better understanding. Acknowledgments We would like to acknowledge University Postgraduate Research Scholarship Scheme awarded to Mr. Jia Geng Boon.
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