Pinus nigra Arnold

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Bioresource Technology 99 (2008) 2893–2897

The manufacture of particleboards using mixture of peanut hull (Arachis hypoqaea L.) and European Black pine (Pinus nigra Arnold) wood chips Cengiz Guler *, Yalcin Copur, Cihat Tascioglu Department of Forest Products Engineering, Duzce University, Faculty of Forestry, 81260 Duzce, Turkey Received 2 February 2007; received in revised form 11 June 2007; accepted 11 June 2007 Available online 3 August 2007

Abstract This research was conducted to investigate the suitability of peanut hull to produce general purpose particleboards. A series of panels were produced using peanut hull and mixture of peanut hull and European Black pine wood chips. Particleboards were manufactured using various hull ratios in the mixture (0%, 25%, 50%, 75% and 100%). Urea formaldehyde adhesive was utilized in board production and boards were produced to target panel’s density of 0.7 g/cm3. Panels were tested for some physical (water absorption and thickness swelling), chemical (holocellulose content, lignin content, alcohol-benzene solubility, 1% NaOH solubility, hot water solubility and cold water solubility) and mechanical (modulus of rupture, modulus of elasticity and internal bond) properties. The main observation was that increase in peanut hull in the mixture resulted in a decrease in mechanical and physical properties of produced panels and panel including 25% hull in the mixture solely met the standard required by TS-EN 312 standard. Conclusively, a valuable renewable natural resource, peanut hull could be utilized in panel production while it has been mixed to the wood chips. 2007 Elsevier Ltd. All rights reserved. Keywords: Particleboard; Peanut hull; Black pine; Chemical properties; Technological properties

1. Introduction The raw material demand of the forest industry increases annually. On the other hand, industrial wood production from the natural forests decline and that forces the forest industry to find some other alternative lignocellulosic biomass as an alternative raw material in the production. Therefore, alternative bio-based materials, recycling, more efficient conversion, and new products are expected to play an important role in the future for the forest industry. The use of renewable biomass (agro-fibers) as a raw material in composites production was one approaches and the use of renewable biomass may result in several ben-

*

Corresponding author. Tel.: +903805413723/138; fax: +903805413778. E-mail address: [email protected] (C. Guler).

0960-8524/$ - see front matter 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2007.06.013

efits such as environmental and socioeconomic (Rowell, 1995). Today renewable biomass are mostly accepted as waste materials and are mostly ploughed into the soil or burnt in the field. It seems that the use of renewable biomass in the forest industry will gain more importance. There are already more than 30 plants that utilize renewable biomass in production of particleboards around the world (Bektas et al., 2005). Therefore, it seems that the number of plants using renewable biomass in production will be more in the future. Following summarizes the studies that examine the suitability of renewable biomass in production. Sunflower stalks (Gertjejansen, 1977; Khristova et al., 1998; Guler et al., 2006), wheat cereal straws (Mosesson, 1979; Han et al., 1998), bagasse (Turreda, 1983), kenaf (Grigoriou et al., 2000), bamboo (Rowell and Norimoto, 1988), waste of tea leaves (Yalinkilic et al., 1998), date palm leaves (Nemli et al., 2001), kiwi pruning (Nemli et al., 2003),

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cotton stalks (Guler and Ozen, 2004), cotton carpel (Alma et al., 2005) and hazelnut husk (Copur et al., 2007) have already been studied by several researchers. Almost 18.5 million tons of peanut has been harvested annually in the world. Therefore, around 7 million tons of peanut hulls left. Peanut (Arachis hypogaea L.) naturally is grown in different regions of Turkey. Peanut are planted more than 30 ha in Turkey and almost 80 thousand tons of peanut hull was produced annually (Cigdem and Gurdal, 2005). Raj et al. (1992) studied the suitability of peanutshell and peanut-hull in composite production. Literature includes only limited information about the feasibility of using peanut hull in composite panel production. Therefore, the objective of this study is to examine the suitability of peanut hull in three-layer particleboard production.

2. Methods Raw materials, peanut hull and European Black pine (Pinus nigra Arnold) woods chips were collected from the field right after peanut (Arachis hypoqaea L.) harvest and Du¨zsan Inc. Du¨zce-Turkey, respectively. Peanut hull were first cleaned from dust and dirt. Later, peanut hull was chipped in a Conduct chipper. Peanut hull and pine wood chips were then classified in a horizontal screen shaker. Particles that remained between 3–1.5 mm sieve and 1.5– 0.8 mm sieve were utilized in the core and outer layers, respectively. Particles were oven dried at 110 C to reach the target moisture content (3%). Urea formaldehyde (UF) resin was used as an adhesive in production and 8% and 10% adhesive levels were used for the core and outer layers based on oven dry weight, respectively. The properties of the UF resin are given in Table 1. One-percent ammonium chloride (NH4CL) was also added to the resin as a hardener. The chips were placed in a drum blender and sprayed with urea formaldehyde and ammonium chloride for 5 min to obtain a homogenized mixture. Panels were designed consisting of 35% face and 65% core layers. Panels were produced to the target density of 0.70 g/cm3. Two panels were produced for each group. The experimental design is shown in Table 2. The dimensions of the produced Table 1 Properties of the UF adhesive Properties

UFa

Solid (%) Density (g/cm3) pH Viscosity (cps) Ratio of water tolerance Reactivity Free formaldehyde (%) 33% NH4Cl content (max, %) Gel point (100 C) Storage time (25 C, max day) Flowing point (25 C)

55 ± 1 1.20 8.5 160 10/27 35 0.15 1 25–30 90 20–40

a

Urea formaldehyde.

Table 2 Experimental design Board typea

A B C D E

Raw material Peanut hull

Pine chips

100 75 50 25 –

– 25 50 75 100

a The density of the boards made from peanut hull and European Black pine wood chips was 0.70 g/cm3.

Table 3 Production parameters of particleboards Parameter

Value

Press temperature (C) Pressing time (min) Peak pressure (N/mm2) Thickness (mm) Dimensions (mm) Outer layer (whole of board %) Middle layer (whole of board %) Number of board for each type

150 7 2.4–2.6 19 480 · 480 35 65 2

particleboards were 48 · 48 · 2 cm in pressing and after edge trimming the final dimensions of the particleboards were to 45 · 45 · 2 cm. The panel production parameters were also displayed in Table 3. Some physical; water absorption and thickness swelling (EN 317, 1996) and mechanical; modulus of rupture (EN 310, 1996), modulus of elasticity (EN 310, 1996) and internal bond (EN 319, 1996) strength properties were determined for the produced particleboards. Test samples for thickness swelling and water absorption were prepared from samples that were formerly tested for modulus of rupture and elasticity. The averages of 10 and 20 measurements were reported for mechanical and physical properties, respectively. The obtained data were statistically analyzed by using the analysis of variance (ANOVA) and Duncan’s mean separation tests. The chemical properties of the peanut hull was also determined and specimens were sampled and prepared according to Tappi T 257 cm (1985) standard. Holocellulose and cellulose contents were determined according to the chloride method (Wise and Karl, 1962). The lignin T 222 om (1998) and ash T 211 om (1993) contents were also studied. Alcohol-benzene T 204 cm (1997), cold and hotwater T 207 om (1999) and 1% NaOH T 212 om (1998) solubility were determined. 3. Results and discussion Table 4 shows the results of ANOVA and Duncan’s mean separation tests for water absorption and thickness swelling for 2 and 24 h water immersion times. The highest water absorption (63.29% and 73.90%) and thickness


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Table 4 Thickness swelling (TS) test results of ANOVA and Duncan’s mean separation tests of particleboards produced from Peanut hulls Physical properties

Board type

Soaking time (min)

Mean (%)a

Std. deviation

Std. error

XMinb

XMaxc

pd

Thickness swelling (TS)

A B C D E A B C D E

2 2 2 2 2 24 24 24 24 24

11.46p 13.78s 13.35s 12.92s 10.16u 15.34t 19.84v 18.89v 17.72w 12.66x

2.706 1.434 1.632 1.501 0.675 1.790 1.609 2.235 1.634 0.689

0.605 0.321 0.365 0.336 0.151 0.400 0.360 0.500 0.365 0.154

7.48 10.17 10.33 10.65 9.24 11.42 16.10 14.42 14.38 11.48

20.88 16.33 16.57 16.52 11.49 18.51 22.25 23.04 20.45 14.33

* * * * * * * * * *

Water absorption (WA)

A B C D E A B C D E

2 2 2 2 2 24 24 24 24 24

57.95p 63.29s 60.35u 55.21t 53.60t 67.85v 73.90w 71.39x 65.95v 61.77z

3.637 2.861 2.752 2.502 2.698 2.667 3.075 2.651 2.717 2.806

0.813 0.640 0.615 0.560 0.603 0.596 0.688 0.593 0.608 0.627

53.20 57.80 55.64 49.09 45.94 63.10 68.52 65.25 59.91 53.16

63.69 68.23 65.79 58.90 58.26 74.20 78.66 75.33 68.64 65.89

* * * * * * * * * *

a

Mean values are the average of 20 specimens. Minimum value. c Maximum value. d Significance level of 0.001 (for ANOVA). p,s,u,t,v,w,x,y,z Values having the same letter are not significantly different (Duncan test). b

swelling (13.78% and 19.84%) were observed with the particleboard (B) having 75% hull in the mixture for 2 and 24 h water immersion times, respectively. Increase in peanut hull percentage in the mixture resulted in a higher thickness swelling and water absorption for particleboards produced using hull and wood chip mixtures. The thickness swelling percents of the panels depends on several factors such as insufficient resin content and distribution, insufficient furnish moisture, poor compatibility of the furnish and adhesive, chemical composition of the furnish, etc. Lower thickness swelling observed for panel type A compared to the panel type B could be explained by the compatibility of the furnish and adhesive. The observed results indicated that the particleboards (A, B, C, and D) including hull in the mixture resulted in higher thickness swelling (more than 14%) required by TS-EN 312 (2005) standard. The water repellent chemicals such as paraffin could be utilized to improve these properties of the panels. Similar results have been reported for the particleboards that are produced using agricultural residues such as 60.7% for the tobacco and tea leaves (Kalaycioglu, 1992) and 35% for cotton stalks (Guler and Ozen, 2004), 19.6% hazelnut hull (Copur, 2007) at 24 h water immersion time. Table 5 shows the results of mechanical properties for produced particleboard. The highest MOR (15.54 N/ mm2) and MOE (2145.71 N/mm2) values were measured for particleboard that was produced using solely pine wood chips. On the other hand, the lowest MOR (9.90 N/mm2) and MOE (1276.76 N/mm2) values were obtained for panels including only peanut hull. Results indicated that

increase in peanut hull in the mixture significantly decreased the mechanical properties of the particleboards. The standard method TS-EN 312 (2005) recommends a minimum MOR and MOE values of 11.5 N/mm2 and 1600 N/mm2 for the particleboards manufactured for general propose-use, respectively. Therefore, the findings of this study resulted in that both panel type D and E met the minimum that the standard required. In case of IB, similar to the other mechanical properties, the highest and the lowest IB values of 0.503 N/mm2 and 0.316 N/mm2 was obtained for the particleboards consisting of solely pine and solely peanut hull, respectively. On the other hand, all produced particleboards met the minimum IB of 0.24 N/mm2 required by the standards for general purpose end-use. This finding is also compatible with previous literature (Kozlowski and Piotrowski, 1987; Goker et al., 1993; Akbulut, 1995; Chow et al., 1996; Bektasß et al., 2002). Certain chemical properties of the peanut hull and some other crop residues and soft/hardwoods were listed in Table 6. A comparison between peanut hull and other crops; hazelnut hull (Copur et al., 2007), cereal straw (Erog˘lu, 1988), cotton carpel (Alma et al., 2005), and softwoods and hardwoods Sjostrom (1993) indicated that the holocellulose content peanut hull was close to the other crop residues and wood species. Exception observed when comparison made with hazelnut hull including lower amount of holocellulose (Table 6). The lignin content peanut hull was higher than cereal straw and cotton carpel, but it was lower when compared with hazelnut hull.

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Table 5 The mechanical properties of particleboards made from Peanut hulls and European Black pine and the test results of ANOVA and Duncan’s mean separation tests Mechanical properties 2

MOR (N/mm )

MOE (N/mmp)

IB (N/mmp)

Board type

Meana

Std. deviation p

Std. error

XMinb

pd

XMaxc

A B C D E

9.90 10.18p 11.32p 14.10s 15.54s

1.049 1.397 0.909 1.517 0.776

0.469 0.625 0.407 0.678 0.347

8.50 8.50 10.60 12.20 14.94

11.40 11.90 12.70 16.20 16.56

*

A B C D E

1276.76p 1356.62p 1459.38p 1885.00s 2145.71u

53.340 218.852 208.738 178.847 135.282

23.855 97.874 93.350 79.983 60.500

1229.70 1095.00 1260.10 1611.30 1997.46

1367.00 1568.20 1776.50 2103.10 2294.62

*

0.026 0.028 0.030 0.026 0.014

0.010 0.011 0.011 0.010 0.005

0.316p 0.322ps 0.350p 0.484u 0.503u

A B C D E

0.276 0.285 0.313 0.457 0.480

* * * *

* * * * *

0.348 0.363 0.386 0.526 0.520

* * * *

a

Mean values are the average of 10 specimens. Minimum value. c Maximum value. d Significance level. p,s,u,v Values having the same letter are not significantly different (Duncan test). * Significant at 0.001 for ANOVA. b

Table 6 Chemical composition of peanut hull (current), hazelnut husk, cereal straw, cotton carpel and soft/hardwoods (Copur et al., 2007) Raw material

Peanut hull Hazelnut husk Cereal straw Cotton carpel Pinus nigra Hardwoods Softwoods

Holo-cellulose (%)

68.8 55.1 64–71 71.6 64.7 70–78 63–70

a Cellulose (%)

42.5 34.6 35–39 42.5 35.5 45–50 45–50

Lignin (%)

28 41.4 12–17 20.5 33 30–35 25–35

Alcohol-benzene solubility was close to cotton carpel and higher than the other crop residues. 1% NaOH solubility was higher than wood species and lower than other crop residues. Hot water solubility was similar to cereal straw and cotton carpel. Cold water solubility of peanut hull was higher than others except hull. 4. Conclusions This study investigated the feasibility of using peanut hull in the manufacture of three-layer particleboard. The results showed that it is possible to produce particleboards using mixture of peanut hull and pine wood chips while using urea–formaldehyde as an adhesive. The amount of peanut hull is at most should be 25% in the mixture to meet the standards required for MOR and MOE. Higher peanut hull in the mixture decreased the mechanical properties and the produced panels were not met the minimum value required by the standard. In addition peanut hull decreased the physical properties of the panels. The physical properties of the panels could be improved using hydrophobic

Ash (%)

– 8.23 3.12 5.54 0.9 0.35 0.35

Solubility (%) Alcohol-benzene (2/1)

1% NaOH

Hot water

Cold water

7 2.0 2–4 6.63 2.5 2–6 2–8

33.5 50.4 38–40 48.6 19 14–20 9–16

11.75 20.9 12–17 12.2 2.25 2–7 3–6

17 18.2 4–7 8.39 3.88 4–6 2–3

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