Properties of thermomechanical pulps derived from sugarcane bagasse and oil palm empty fruit bunches

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Properties of thermomechanical pulps derived from sugarcane bagasse and oil palm empty fruit bunches Lilik Tri Mulyantara a,b , Harsono Harsono b , Roni Maryana a,c , Guangfan Jin d , Atanu Kumar Das a,e , Hiroshi Ohi a,∗ a

Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan Center of Agricultural Engineering Research and Development, Ministry of Agriculture, Indonesia c Technical Implementation Unit for Chemical Engineering Processes, Institute of Sciences, Indonesia d School of Light Industry, Zhejiang University of Science and Technology, China e PT. Indah Kiat Pulp & Paper Tbk, Perawang Mill, Indonesia b

a r t i c l e

i n f o

Article history: Received 9 September 2016 Received in revised form 1 November 2016 Accepted 2 November 2016 Available online xxx Keywords: Thermomechanical pulp Sugarcane bagasse Oil palm empty fruit bunch Tensile index Bending strength

a b s t r a c t This research identified suitable conditions to fabricate pulp fibers for paperboards and medium density fiberboards (MDF) from the bagasse of sugarcane (Saccharum officinarum) and the empty fruit bunch (EFB) of oil palm (Elaeis guineensis). First, the effects of chemical pretreatments at 121 ◦ C and pressurized refining under steaming conditions were studied in regards to the thermomechanical pulps. The optimal conditions to achieve the highest paper strength properties of the EFB pulp involved pretreatment with 2% NaOH for 2 h and refining at 0.7 MPa of pressure at 165 ◦ C. The sugarcane bagasse (SB) pulp properties could not be improved by chemical pretreatment, while the EFB pulp properties clearly benefited from such pretreatment. Second, the effects of dry and wet blowing methods after pressurized refining on the fiber properties were examined. The strength properties of the half-dried SB and EFB pulps with 55% solid content were slightly higher than those of their wet counterparts. These results clearly suggest that SB and EFB can be promising refined fibers for paperboard and MDF preparation. Third, MDF was made from dried EFB refined fibers with 92% solid content by dry processing, and suitable properties for actual use were obtained. © 2016 Elsevier B.V. All rights reserved.

1. Introduction In 2014, Indonesia produced 2.8 million tons of cane sugar from 36 million tons of sugarcane (Saccharum officinarum) in 0.47 million ha of harvested area (Statistic Indonesia Bureau, 2014). The production of sugar from sugarcane yields the fibrous by-product sugarcane bagasse (SB), which is typically combusted in furnaces to produce steam for power generation. Because of this, SB is one of the most useful agricultural biomasses in that region. Indonesia is also the largest producer of palm oil in the world. In 2013, approximately 26 million tons of crude palm oil was produced, and about 30 million tons of empty fruit bunches (EFB) are produced each year from the oil palm (Elaeis guineensis) (Harsono et al., 2015, 2016).

Abbreviations: TMP, thermomechanical pulp; MDF, medium density fiberboards; EFB, empty fruit bunch; SB, sugarcane bagasse; MOR, modulus of rupture. ∗ Corresponding author at: University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8572 Japan. E-mail addresses: lilik [email protected] (L.T. Mulyantara), roni [email protected] (R. Maryana), [email protected] (H. Ohi).

Researchers have recently studied SB and EFB for their efficient use in various applications such as bio-ethanol, particleboards, and plant media. These studies were partially motivated by the fact that SB and EFB are fully biodegradable, light, abundant and renewable raw materials in high supply (Cardona et al., 2010; Das et al., 2014; Singh et al., 2013). Both unbleached and bleached SB chemical pulps obtained by soda, soda-anthraquinone (AQ) and alkaline sulfite-AQ (AS-AQ) cooking had tensile and tear indices greater than 50.0 N m/g and 5.5 mN m2 /g, respectively (Khristova et al., 2006; Banavath et al., 2011; Agnihotri et al., 2010). Of these, the highest tensile index was obtained by AS-AQ cooking (Hedjazi et al., 2008), and the quality of corrugated board materials made using a neutral sulfite semi-chemical SB pulp was investigated (Khakifirooz et al., 2013). While there have been reports on the properties of fiber particles and mechanical pulps prepared under atmospheric pressure from non-wood fibrous materials, the properties of thermomechanical pulp (TMP) obtained specifically from SB and EFB of oil palm have not been clarified. Xavier et al. (2013) studied the bending stiffness component of medium density fiberboard (MDF) panels from mixtures of SB particles (unrefined fibers) and eucalyptus refined fibers. From these, they made particleboard by dry process but did

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not clarify the fiber length fractionation. Belini et al. (2012) studied panels made from mixture of SB particles (unrefined fibers) and eucalyptus refined fibers, using dry process to make the panels. Hoareau et al. (2006) studied fiberboard based on SB lignin and fibers, focusing on the SB fibers impregnated with some chemical and fiberboard using SB lignin to substitute of phenol, but they did not detail the fabricating process of the fiberboard. Despite these previous studies, the conditions for producing SB and EFB fibers suitable for MDF are not known. Fibers for MDF are typically prepared by using a disk-refiner under pressurized steaming conditions at 160–175 ◦ C, which is similar to how paper-grade TMP is made. However, MDF fibers are directly dried immediately after refining followed by blending with adhesives. The main purpose of TMP processing with wood is to separate the fibers to make them usable for papermaking (Illikainen, 2008; Kang et al., 2006). In the TMP process, pressurized steam is applied before and during refining to raise the wood temperature, softening the lignin in the process. When the temperature is high enough to soften the lignin, but not so high that the lignin spreads over the fiber surface, the fibers can be torn from the matrix in such a way that the secondary cell wall layers (S1 and S2 layers) are exposed. In the production of chemi-thermomechanical pulps (CTMP), lignin is softened by chemical treatment and increased temperatures. Fibers prepared from reed and wheat straws, and the MDFs obtained from such fibers, have been previously studied using a pressurized refiner (Han et al., 2001). In these experiments however, the refiner plate gap was 0.37 mm. The wide refiner gap implies that fibers with the desired properties cannot be produced. The properties of wheat straw and soybean straw fibers, and their resulting MDFs, have been previously investigated using an atmospheric refiner (Ye et al., 2007). Here, the fibers were prepared at atmospheric pressure and then collected by a wet blowing method. Properties of MDF produced from rice straw fibers obtained using a pressurized refiner (plate gap: 0.508 mm) and a wet pulp blowing method have been studied elsewhere (Li et al., 2013), but fibers with the desired properties cannot be produced in this instance. Elsewhere, wheat straw fibers were studied using a fully equipped pilot plant to produce fibers by a pressurized refiner, with a continuous drying method and a continuous mixing of resins, and the properties of these fibers and prepared MDFs were investigated (Halvarsson et al., 2008). When clarifying the properties of fibers used as paperboard and MDF materials, it is important to have a refiner plate gap on the scale of a single fiber width, appropriate pressure and temperature conditions for refining, and to select a dry blowing method that provides low-moisture fibers for MDF material. From this viewpoint, the previous study using wheat straw (Halvarsson et al., 2008) is important; however, there are no studies examining the use of SB and EFB in this manner. The back ground of this study seeks to expand the usage of SB and EFB, waste materials generated in the sugar and palm oil industries, by identifying the conditions needed to make fibers suitable for use in products such as paperboard and MDF. This study was conducted to improve the fiber properties through chemical pretreatment and pressurized refining with a thermomechanical refiner for fabricating SB and EFB paperboard and MDF, and the conditions for obtaining suitable fibers were determined.

2. Materials and methods 2.1. Materials preparation The SB and EFB used in this study were obtained from PT. Madukismo in Yogyakarta, Indonesia and PT. Perkebunan Nusantara VIII in Bogor, West Java, Indonesia, respectively. SB was washed twice

manually and dried in direct sunlight to a moisture level of 8–10%. Dried SB was cut into 0.5–2.0 cm by a shredding machine, while EFB was cut into 0.5–4.0 cm by a laboratory disk mill. Based on original shapes of SB and EFB, material-cut dimensions are not specific other than for length. Wood chips of mixed light hardwoods (MLH) for MDF provided by Hokushin Co., Ltd. Kishiwada, Osaka, Japan, and a softwood (Larch: Larix leptolepis) obtained from the Agricultural and Forestry Research Center of University of Tsukuba, Yatsugatake Forestry, Kawakami, Nagano, Japan were used for comparison, with dimensions of 2 cm × 2 cm × 0.4 cm (length × width × thickness). 2.2. Chemical pretreatment Materials (300 g as oven-dried weight) were soaked with water containing 0–4 wt% Na2 SO3 or 2 wt% NaOH (based on oven-dried weight), using an autoclave at 121 ◦ C for 2 h. Due to the bulkiness of the fibers, the liquid to fiber ratio was 7 L/kg, while the liquid to wood ratio was 4 L/kg. After pretreatment, the yield loss and pH of the liquid were determined. 2.3. Thermomechanical pulping The pretreated materials were treated under pressurized steaming conditions using a laboratory pressurized single disk refiner with a refiner plate (Type J) 305 mm in diameter (model BRP45300SS manufactured by Kumagai Riki Kogyo Co., LTD., Nerima, Tokyo), equipped with a steam boiler (model SU-200 supplied by MIURA Co., LTD., Matsuyama, Ehime). The temperature of the refiner was 140 or 165 ◦ C, with supplied steam pressures of 0.5 and 0.7 MPa respectively. The temperature was increased over a 10 min span, and the refiner was held at the maximum temperature for 2 min. Refinement was conducted at a rotation speed of 3000 rpm. The disk clearance (plate gap) of the refiner was adjusted to 0.10 mm based on previous studies (Harsono et al., 2015). A smaller gap in the grinder produces more external fibrillation in the fibers of non-woody materials, which could benefit the physical properties of the pulp (Kang et al., 2006). The second refining (beating) was conducted using a PFI mill (ISO 5264-2:2011) at 10,000 revolutions to make fibers suitable for paperboard based on conditions used previously (Harsono et al., 2015). As fibrous materials, SB and EFB have certain difficulties when used as supply materials for feeding processes, compared to wood chips. To improve their feeding efficiency in screw conveyors, pressurized steam was blown in a controlled switching manner to push these materials into the disk region. Two types of pulps were obtained depending on the blowing method used, labeled as “halfdried pulp” with 32–55% solid contents (SC) and “wet pulp” with SC <10%. For the half-dried pulp, the refined fibers were vented from the refining chamber through a blow line into a blow box consisting of four sides with 60 mesh wire (250 ␮m opening), while for the wet pulp the fibers were discharged into a blow tank. 2.4. Evaluation of pulp properties Classification of the refined fibers was conducted according to a pulp test method with a Bauer McNett Fiber Classifier No. 2593 using 1180, 600, 300, 150 and 75 ␮m opening screens (14, 28, 48, 100, and 200 mesh, respectively) at the School of Light Industry, Zhejiang University of Science and Technology. The refined pulp was further treated with a PFI mill at 5000 to 12,500 revolutions according to ISO 5264-2:2011. Forming hand sheets for physical tests of the pulp followed the ISO 5269-1:2005 standard. The physical properties, as well as the tensile and tear indices of the handsheets, were determined according to ISO 1924-2:2008, 1974:2012, and 5270:2012 standards. The length and width of the

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Table 1 Experimental design. Refininga

Pretreatment

PFI

Material

Chemical

Dosage (%)

Temp. ( C)

Time (h)

Clearance (mm)

Temp. at press. (◦ C at MPa)

Time (min)

Blowing method

(rev.)

SB EFB MLH Larch

Na2 SO3 NaOH

0 2 4

121

0 2 3

0.10

40 at 0 140 at 0.5 165 at 0.7

2

Half-dried Wet

5000 7500 10,000 12,500

a

◦

Rotation speed: 3000 rpm.

pulps were also determined using a Lorentzen-Wettre fiber tester CODE 912. These experimental design are summarized in Table 1.

2.5. Chemical analysis of materials Materials were milled with a Wiley mill and sieved to retain particles 40–80 mesh in size. These were stored at room temperature and air-dried, and Soxhlet-extracted with acetone. The contents of the acid-insoluble lignin (Klason lignin), acid-soluble lignin and ash were determined using TAPPI Test Method T 222 om-15 and T 211 om-02, and the amounts of glucose and xylose in the acid hydrolysate were determined using ion chromatography according to previously published procedures (Harsono et al., 2016).

2.6. MDF fabrication from EFB and the properties EFB TMP with approximately 92% solid content was prepared according to a modified method reported previously (Mulyantara et al., 2016), and MDF was fabricated with 5% methylene diphenyl diisocyanate, 0.8% polyol, and 0.5% wax. The mixture was coldpressed and hot-pressed at 180 ◦ C and 3 MPa and at 0.5 MPa for degassing. A piece of MDF 350 × 350 × 2.7 mm3 in size (after polishing) with a target density of 780 kg/m3 was conditioned at 20 ◦ C and 65% RH for one week, after which the density, modulus of rupture (MOR), modulus of elasticity (MOE), and internal bonding (IB) were determined. Thickness swelling (TS) and water absorption (WA) after immersion in water at 20 ◦ C for 24 h were determined.

3. Results and discussion 3.1. Chemical compositions of SB and EFB raw materials The lignin and glucan (cellulose) contents of the raw materials were 25.0% and 41.2% for SB, and 29.6% and 35.1% for EFB, respectively (Table 2).

3.2. Effect of pretreatment on yield loss We expect softening and swelling effects on the cell walls of these materials after chemical pretreatment. Most of the lignin and cellulose do not react under mild conditions, except for a small extention of lignin sulfonation with Na2 SO3 pretreatment, because the conditions of these chemical pretreatments are not so strong compared to those of chemical cooking. As shown in Table 3, increasing the Na2 SO3 dosage causes yield loss. Increased alkali dosage also caused decreased chemimechanical pulp yield of bagasse and canola straw (Khakifirooz et al., 2013; Fatehi et al., 2011). This yield loss is caused by reduced amounts of hemicellulose, organic acid and ash (Harsono et al., 2015). Soaking these materials in a 2% NaOH solution significantly affected the properties of tropical bamboo mechanical pulp (Ashaari et al., 2010).

Fig. 1. Correlation between density and tensile index of paperboards.

3.3. Properties of chemical pretreated thermomechanical pulp for paperboard 3.3.1. Effect of chemical pretreatment on pulp properties The addition of 2% Na2 SO3 or 2% NaOH to pretreatment had a positive effect on the properties of EFB refined pulp, but had a negative impact on the properties of the SB pulp (Table 4). When pretreated with 2% NaOH, the tensile and tear indices of the EFB pulp improved to 23.1 N m/g and 5.46 mN m2 /g, respectively. It has been previously reported that soaking wood with certain chemicals can adversely affect its properties (Hillis, 1984). The SB pulp with a chemical-free pretreatment had the highest tensile and tear indices with values of 22.0 N m/g and 3.82 mN m2 /g respectively. SB with a chemical-free pretreatment might be sufficient to soften the lignin in fibers. On the other hand, under the same pretreatment and refining conditions, the EFB pulp had tensile and tear indices of 14.6 N m/g and 3.61 mN m2 /g, respectively. TMP made from SB exhibited higher tensile and tear indices compared to EFB pulp with a chemical-free pretreatment. The disadvantage of extremely low strength properties was not observed for SB and EFB pulps compared to the MLH and Larch wood pulp control samples (Fig. 1). In addition, the ISO brightness values of the SB and EFB pulps were similar to those of the Larch wood and MLH pulps, respectively. 3.3.2. Effect of post-refinement blowing methods on pulp properties Handsheets of the half-dried SB and EFB pulps had slightly higher tensile and tear indices compared to their respective wet pulps (Table 4). The results of fiber fractionation (Table 5) show that SB and EFB half-dried pulps had smaller ratios of the largest fiber fractions (>1180 ␮m opening) than the wet pulps. Increasing the contents of the smallest fine (<150 ␮m opening) fractions is expected to increase the density and tensile strength of SB and EFB pulp sheets. Fines from chemical pulps were previously demonstrated to increase the strength of fiber-to-fiber bonds, enhancing the density as well as the tensile strength of pulp sheets (Marie et al., 2008). This fiber fractionation can be explained by effects from

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Table 2 Chemical compositions of SB and EFB raw materials.

SB EFB a b c d

Acid-insoluble (soluble) lignin (%)

Glucana (%)

Xylan (%)

Other sugarsb (%)

Extractivesc (%)

Ash (%)

Other organicsd (%)

23.9 (1.1) 26.7 (2.9)

41.2 35.1

18.5 19.8

2.4 1.9

1.3 5.4

1.6 5.9

10.0 2.3

As polymer of glucose. As polymer of arabinose, galactose and mannose. Acetone extractives. Organic acids and other extractives.

Table 3 Effects of chemical pretreatment on liquid pH and yield loss. Material

SB – EFB a

Chemical

Dosage (%)

After pretreatment at 121 ◦ C for 2 h Liquid pH

Yield (%)a

–Na2 SO3 Na2 SO3 NaOH

0 2

2

4

4.135.275.45 6.07

96.295.794.2 95.9

–Na2 SO3 Na2 SO3 NaOH

0 2

2

4

6.406.606.90 8.12

94.994.893.5 94.7

Yield after pretreatment, based on raw materials.

the pretreatment and refining conditions. SB or EFB pulps with no chemical pretreatment had a larger ratio of the smallest (<150 ␮m opening) fraction compared to other SB or EFB pulps. The addition of these chemicals softens the fibers and suppresses the formation of the finer structures. Unfortunately, we found that the refining temperature sometimes decreased to approximately 120 ◦ C during refining due to the repeated pressurized steam flow used to push the materials into the disks. It has been reported that the differences between sheet properties of hardwood and softwood pulps arise not only from the average fiber length but also from fine fiber characteristics (Kamijo et al., 2015); the densities and tensile indices of handsheets could be improved by addition of fine fractions to the pulps (Kamaluddin et al., 2012). Compared with the results of fiber characterization from mill MLH pulps, SB and EFB pulps having smaller ratios of long fiber fractions (>1180 ␮m opening) and containing shives were obtained.

ing of the fibers, making them easier to refine and improving their physical properties (Salmen, 1984; Fernando et al., 2011; Muhic, 2010). Increased temperatures also enhance fibrillation, leading to better single fiber properties (Aisyah et al., 2013). High temperatures could lead to very low strength poorly bonding pulps when it would otherwise be high enough that the lignin spreads over fiber surfaces. In the preparation of SB pulps, a chemical-free pretreatment, thermomechanical refining at 165 ◦ C and a half-dried blowing method provided the best paper strength properties of the resulting pulp sheets. In the preparation of EFB pulps, pretreatment with 2% NaOH, thermomechanical refining at 165 ◦ C and a half-dried blowing method provided the best paper strength properties of the resulting pulp sheets.

3.4. Effect of refining temperature on pulp physical properties

As shown in Table 7, MOR, MOE and IB of the EFB MDF were 18.5, 1649 and 1.4 N/mm2 , respectively. The MOR and MOE were suitable for actual use, but still lower than those of commercial MDFs industrially produced from MLH. The IB and TS were suitable to the minimum requirement of JIS A 5905:2003 for fiberboards.

Refining can improve the bonding ability of fibers, forming strong and smooth paper with good printing properties (Lei et al., 2010). Refining can not only separate fiber walls, but also create finer fibers through cutting and shortening, as well as external and internal fibrillation. This is caused by the partial removal of the primary wall, bringing the secondary wall into direct contact with water; water absorption promotes swelling which improves the fiber flexibility. Flexibility governs many physical and optical properties of pulp and paper, including paper formation (Fernando et al., 2011), and therefore control over the flexibility is of vital importance. In the refining process, these fibers are typically exposed to compression and shear forces, which alter the fibers (Gharehkhani et al., 2015). As shown in Table 6, the refining process of half-dried SB and EFB pulps at 165 ◦ C resulted in stronger pulp sheets compared to the 140 ◦ C process. The strength of wet EFB pulp at 165 ◦ C was similar to that at 140 ◦ C, while the strength of the wet SB pulp at 140 ◦ C was higher than that at 165 ◦ C. Using a half-dried blowing method, increasing the temperature improved the physical properties of the resulting paperboard. It has been reported that the temperature and moisture present during refining are key factors affecting fibers separation and development, due to the softening and viscoelastic behavior provided to the wood material (Illikainen, 2008). High temperatures before and during refining contribute to soften-

3.5. Properties of MDF fabricated from EFB TMP

4. Conclusions The optimum thermomechanical pulping conditions for EFB involved pretreatment with 2% NaOH at 121 ◦ C for 2 h and thermomechanical refining at 165 ◦ C, 0.7 MPa and a 0.10 mm disk clearance with a half-dried blowing method. Meanwhile, with a chemicalfree pretreatment under the same thermomechanical refining and blowing conditions, the resulting SB pulp had its highest tensile and tear indices. The tensile indices of SB and EFB pulps obtained under these conditions were 22.0 and 23.1 N m/g. The relationship between the fiber properties and the solid content of the pulp fibers blown into the atmosphere just after pressurized refinement were examined. The strength properties of SB and EFB half-dried pulps having 55% solid contents were slightly higher than those of the SB and EFB wet pulps. These results clearly suggest that SB and EFB can be fabricated into promising pulp fibers for raw materials of paperboard and MDF. MDF was successfully made from dried EFB refined fibers with 92% solid content by dry processing, and the suitable properties for actual use were obtained.

Please cite this article in press as: Mulyantara, L.T., et al., Properties of thermomechanical pulps derived from sugarcane bagasse and oil palm empty fruit bunches. Ind. Crops Prod. (2016), http://dx.doi.org/10.1016/j.indcrop.2016.11.003

Pulp propertiesc

Chemical dosage

Blowing method e

CSF (mL)

Fiber lengthd (␮m)

Density (g/cm3 )

Tensile index (N m/g)

Tear index (mN m2 /g)

Brightness (% ISO)

SB

S1 S2 S3 S4

None 2% Na2 SO3 2% NaOH 2% NaOH

Half-dried Half-dried Half-dried Wet

215 388 415 219

550 449 542 517

0.507 0.429 0.394 0.519

22.0 14.0 13.7 13.6

3.82 2.77 3.00 2.73

32.3 37.6 36.6 35.2

EFB

E1 E2 E3 E4

None 2% Na2 SO3 2% NaOH 2% NaOH

Half-dried Half-dried Half-dried Wet

239 284 231 345

410 424 467 565

0.443 0.483 0.516 0.483

14.6 19.1 23.1 22.2

3.61 4.31 5.46 4.37

28.4 29.1 26.3 29.0

MLH Larch

– –

2% NaOH 2% Na2 SO3

Half-dried Half-dried

302 262

478 688

0.389 0.523

8.79 18.9

2.42 6.46

29.7 36.2

a b c d e

Pretreatment conditions: 121 ◦ C, 2 h. Refining conditions: 165 ◦ C, 0.7 MPa, 10 min and 0.10 mm disk clearance. PFI mill beating: 10,000 revolution. Determined using a Lorentzen-Wettre fiber tester CODE 912. Solid content: 55%.

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Table 4 Effects of chemical pretreatment on physical properties of thermomechanical pulps.

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Table 5 Effects of blowing methods on characterization of thermomechanical pulps using screens. Refininga

Classification using screensb

Sample name

Blowing method

CSF (mL)

>1180 ␮m (>14 mesh) (%)

600–1180 ␮m (28–14 mesh) (%)

300–600 ␮m (48–24 mesh) (%)

150–300 ␮m 150 ␮m > (100 (100–48 mesh) mesh>) (%) (%)

SB

S1 S2 S3 S4

Half-driedc Half-dried Half-dried Wet

812 785 788 778

17 ± 0.4 25 ± 0.4 15 ± 0.2 34 ± 0.9

15 ± 0.2 17 ± 0.5 19 ± 0.2 17 ± 0.9

22 ± 0.2 22 ± 0.4 26 ± 0.4 21 ± 0.2

21 ± 1.0 18 ± 0.2 20 ± 0.3 14 ± 1.8

25 ± 0.5 18 ± 0.4 20 ± 0.3 14 ± 1.4

EFB

E1 E2 E3 E4

Half-dried Half-dried Half-dried Wet

768 782 782 780

4 ± 0.4 6 ± 0.4 10 ± 0.4 30 ± 0.5

15 ± 0.4 16 ± 0.3 22 ± 1.2 22 ± 0.3

27 ± 1.0 26 ± 0.5 27 ± 0.3 20 ± 0.1

24 ± 1.1 22 ± 1.5 19 ± 0.7 14 ± 0.1

30 ± 2.4 30 ± 0.6 22 ± 0.4 14 ± 0.4

–

21 ± 0.5

23 ± 1.5

23 ± 1.3

25 ± 0.4

8 ± 0.1

Mill MLH − a b c

Dried ◦

◦

Pretreatment conditions: 121 C, 2 h; Refining conditions: 165 C, 0.7 MPa, 10 min and 0.10 mm disk clearance. Determined using a Bauer McNett Fiber Classifier No. 2593. Solid content: 55%.

Table 6 Effect of refining temperature on pulp physical properties. Pretreatmenta

Refininga

Sample name

Chemical dosage

Temp. (◦ C)

Blowing method

CSF (mL)

Fiber lengthc (␮m)

Density (g/cm3 )

Tensile index (N m/g)

Tear index (mN m2 /g)

SB

S5

140

470

0.358

8.5

2.37

S2

388

449

0.429

14.0

2.77

EFB

E5

390

452

0.439

16.2

4.22

EFB

E2

284

424

0.483

19.1

4.31

SB

S6

140

Halfdriedd Halfdried Halfdried Halfdried Wet

197

SB

168

531

0.450

16.0

3.16

SB

S4

165

Wet

219

517

0.519

13.6

2.73

EFB

E6

140

Wet

308

535

0.484

22.1

4.47

EFB

E4

2% Na2 SO3 2% Na2 SO3 2% Na2 SO3 2% Na2 SO3 2% NaOH 2% NaOH 2% NaOH 2% NaOH

165

Wet

345

565

0.483

22.2

4.37

a b c d

165 140 165

Pulp propertiesb

Pretreatment conditions: 121 ◦ C, 2 h. PFI mill 10,000 revolutions. Determined using a Lorentzen-Wettre fiber tester CODE 912. Solid content: 55%.

Table 7 Mechanical properties of MDF made from EFB TMP. Density (kg/m3 )

EFBMLH a b c d e

769

777

MORa (N/mm2 )

18.5 ± 1.630.8 ± 2.8

MOEb (N/mm2 )

1649 ± 1473006 ± 304

IBc (N/mm2 )

1.4

1.5

Immersion in water 20 ◦ C for 24 h TSd (%)

WAe (%)

11.78.3

32.124.2

MOR: modulus of rupture in static bending. MOE: modulus of elasticity in static bending. IB: internal bond test. TS: thickness swelling. WA: water absorption.

Acknowledgements

References

The authors are grateful for the assistance given by Ms. Yin Ying H’ng in testing the classification of refined fiber fractionation. Particular gratitude is also extended to Dr. Hideaki Takahashi (Hokushin Co., Ltd.) for valuable advice and testing assistance during MDF fabrication. This work was in part supported by the Scholarship Donations of Hokuetsu Kishu Paper Co., Ltd. (Dewaterability of Pulp for Paperboard).

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Please cite this article in press as: Mulyantara, L.T., et al., Properties of thermomechanical pulps derived from sugarcane bagasse and oil palm empty fruit bunches. Ind. Crops Prod. (2016), http://dx.doi.org/10.1016/j.indcrop.2016.11.003