Effect of Beating on Coir Handsheet...

American Journal of Oil and Chemical Technologies; ISSN (online): 2326-6589; ISSN (print): 2326-6570

Volume 2, Issue 1, January 2014

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Effect of Beating on Coir Handsheet Properties

Maria Ulfa1, Wega Trisunaryanti2, Bambang Setiaji3, Triyono4

Department of Chemistry, Universitas Gadjah Mada, Yogyakarta, Indonesia1,2,3,4 Department of Chemistry, Universitas Mataram, Mataram, Indonesia1

Abstract:

Coconut fibers or coir was examined to determine its potential value for pulp and papermaking. Alkali pulping was investigated by using caustic soda on a laboratory scale and then the pulp was beaten in a PFI mill at 0, 750, 1500, 3000 and 10000 revs. Projection microscope and SEM detected the fiber parameters. While, the main mechanical properties of hand sheet produced from soda processes were evaluated on 60 g/m2 test sheets as functions of the following parameters: tensile index and tear index. The results showed at a PFI mill revolution number of 1500 revs, the properties of hand sheet reached the optimum values.

Keywords: alkali pulping; beating; handsheets; tensile index; tear Index

1. Introduction Indonesia paper consumption is increasing so the use of wood as raw material for pulp paper also increase.. Therefore, an alternative material is required which can be used to replace the role of wood in the manufacture of paper pulp, one of them is coir.

Coir from coconut husk represent a type of abundant renewable resources. Various studies have been reported on its fiber dimensions and chemical composition. Coir can also be used as an alternative raw material pulp and paper, because it has chemical composition similar to softwood [1]. As for the chemical composition for hardwood fiber is 36-49, 21-23, and 25-27% respectively for the content of α cellulose, lignin, and hemicelluloses while for fiber is 40-45, 24-27, and 26-27% [2].

Studies on the use of coir as a raw material pulp and paper are very few until now. his may be due to the fibers are brittle in nature and has high content of lignin. In addition, the presence non fiber (pith) which could not be separated perfectly from the fibers. Non-fiber cells have high lignin content, easily soluble in water and can react with residual lignin in the pulp. This causes an increase in kappa number (index of the degree of delignification), decrease in the degree of brightness and the mechanical properties of paper.



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According Joedodibroto [3], the most effective pulping process decreases the amount of lignin and kappa number was the process of soda. In this research, the goal of pretreatment was to separate pith from fibers. To obtain good fiber fibrillation, the pulp was beaten in a PFI mill Beating of chemical pulp is an essential step in improving the bonding ability of fibers, causing a variety of simultaneous changes in fibers, such as internal fibrillation, external fibrillation, fiber shortening or cutting, and fines formation [4] [5].

The present study investigates the properties of coir soda pulp, analyzes fiber morphology and discusses the physical properties of handsheet. As coir may become a papermaking material [1] [3] the study will suggest a new direction in the application of coir.

2. Experimental

Material Coconut husks were collected from the region of Yogyakarta-Indonesia and defibrated by defibrator machine to produce coir fibers. Then, the fibers were thoroughly wetted by soaking in water for about 48 hours to eliminate dust, lignin and pith content.

The coir fibers that have been dried under natural conditions used for this study were cut into small size fraction (5-6 cm length) and extensively washed before being cooked.

Method 1. Measurement of fiber morphology (fiber dimension) Coir fibers with size of about 2 × 2 × 25 mm macerated in 10 mL of solvent HNO3 67% (v/v) and heated in a water bath (100 ± 2°C) for 10 minutes [6]. Samples that have changed color and resemble cotton washed with distilled water repeatedly. Fibers obtained were safranin and cell dimensions were measured using a projection microscope. Dimensions measured were fiber length, fiber diameter, wall thickness and diameter of each fiber lumen measured 30 times, and then calculated the average value.

2. Pulping and beating conditions Coir fibers that contain free pith (± 15% moisture content) were weight and charged into the tube digester capacity of 3 L with the require amount of chemical solution at a liquor to solid ratio 8:1. The digester was heated to the operating temperature (135oC) and time (90 min). As for concentration of cooking liquors were added 15% NaOH (w/w, based on o.d.w). The resulting pulp thoroughly washed with tap water to avoid chunks of fiber (fiber bundles). Further pulp milled and pressed to remove the water content in pulp. Furthermore, the pulp and fibers produced that stored as stock pulp ([7] [8].

The pulps were diluted by distilled water to attack 1.2% consistency, then refine in a PFI mill (TAPPI T 248 sp-00) at 0, 750, 1500, 3000 and 10000 revs. Pulp with different beating



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degrees were obtained. In a subsequent stage, the freeness determined was conducted in accordance with TAPPI T 227.

3. Hand sheets preparation and Characterization The previously refined pulps were then used to prepare paper hand sheets with a basis weight of 60 g/m2, according to TAPPI standard method T 205 sp-95. As recommended by Australian/New Zealand Standard Methods 448s and 437s, the hand sheets were equilibrated at 23oC and 50% relative humidity before testing their physical properties. Then, the basis weight (TAPPI T 410 om-08), thickness (TAPPI T 411 om-10), density and bulk (TAPPI T426 wd-70) were measured.

The important strength properties of paper performed in this study were tensile strength (TAPPI T494 om-01) and tearing resistance (TAPPI T414 om-98). An Instron tensile tester (Instron 5566) was used to record maximum tensile force with constant rate of elongation at 10 mm/min. The tensile index defines the tensile strength was calculated and is equal to tensile strength (N/m) divided by basis weight (g/m2). Tearing resistance was measured with the Messmer Büchel Digi-Tear instrument. Test method is called the “Elmendorf Tear Test”. The tear index for each sample calculated as tear strength (N/m) divided by basis weight (g/m2).

Hand sheet uniformity is often evaluated by viewing a sheet in transmitted light. Formation test was measured with the Paper Perfect Formation Tester (Op Test Equipment Inc. Canada). The tester classifies formation quality in 10 formation components over a specific range and produces the formation value. The relative formation value (RFV) of each component relates to selected reference sheet. RFV values less than 1 means that the formation quality of the tested paper is worse than the formation quality of the reference paper.

The structures of the obtained hand sheets were observed using a Phenom Scanning Electron Microscope (SEM). Each sample was prepared with a gold/palladium coating before the analysis.

3. Result and Discussion

Fiber Properties The ability of coir fibers as raw material for pulp can be determined by measuring the fiber dimensions that contribute to the strength properties of the pulp. Fiber dimensions and derived values of coir fibers and the relevant data from the literature are summarized in Table 1.



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Table 1. RESULT OF COIR FIBERS DIMENSIONS MEASUREMENT AND THE RELEVANT DATA FROM THE LITERATURE

Fiber Dimensions and Derived Values

Coir Coir [9] Oil-palm empty fruit bunc [10]

Bagasse [11]

Length (mm) 1.55 1.43 0.99 1.59 Diameter (µm) 25.91 23.23 19.10 20.96

Lumen width (µm) 16.06 13.26 11.66 9.72 Cell wall thickness (µm) 4.93 4.99 3.38 5.36

Runkel ratio 0.61 0.75 0.58 1.16 Slenderness ratio 59.82 61.55 52.10 76.05

Flexibility coefficient 61.98 57.08 61.05 46.37

Fibers were classified into three groups. The first group was considered short fibers with length of less than 0.9 mm such as hardwood. The second group, like coir, bagasse, oil-palm empty fruit bunc, had an average length between 0.9 to 1.9 mm. The results showed that the average fiber length of coir was 1.55 mm. The third group included fibers longer than 1.99 mm [12]. According to Agopyan [9], categorized fibers had shorter fibers with moderate lumen diameter and fiber wall thin which affect the strength of pulp and paper, because the fibers will form a network less well.

Generally, the acceptable value for slenderness ratio of papermaking fibers are more than 33 [13]. By referring to this and morphological properties of all types of agricultural residues fibers, they are suitable to be used for pulp and papermaking. According to Istas [14] and Bektas [15], there are four different types of fiber which are classified under flexibility ratio: (1) High elastic fibers having elasticity coefficient greater than 75; (2) Elastic fibers having elasticity ratio between 50 to 75; (3) Rigid fibers having elasticity ratio between 30 to 50; and (4) High rigid fibers having elasticity ratio less than 30. According to this classification, flexibility coefficient of coir fibers was 57.08 – 61.98, which fall under elastic fibers group. On studies about softwoods, elasticity coefficient was found as 60.02 for Pinus sylvestris [16], 62.71 for Pinus brutia [14] and 66.92 for Picea orientalis [17]. Examining this information given, it seems that coir fibers were similar to other softwood fibers. By dividing cell wall thickness by lumen diameter, runkel classification value was obtained. When runkel proportion is greater than 1, it indicates that a fiber has thick wall and cellulose obtained from this type of fiber is less suitable for paper production; when it is equal to 1, it specifies that a cell wall has medium thickness and cellulose obtained from this type fiber is suitable for paper production. When the rate is less than 1, it points out that a cell wall is thin and cellulose obtained from this fiber is the most suitable for production of paper [17] [12]. Runkel value of coir was 0.61 - 0.75 and according to the runkel classification, it fall under thin wall fibers group and the most suitable for production of paper.



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Pulp Properties The influence of beating level on drainability of coir soda pulp is presented in Fig.1. Its drain ability slightly reduced when the PFI refining increased from 0 to 10,000 revs because percentage of short fibers increases. However, as the results showed, freeness number of pulp is still high. At high freeness the fibers were not sufficiently fibrillated. Coir cell wall is thick and hard, the primary wall is not easy to be damage. Beside that the fiber has a lumen and many lacunas within its cellular structure as seen as Fig.2. Because of the structure, fiber is very easy to absorb water and swell, so the fiber become flexible and when beating was less likely to be cut and fibrous (Fig.3). That was also very adverse which the fibers lose strength so it was very soft and brittle.

Figure 1. The relationship between freeness and beating levels of coir soda pulp.

Freene

ss (m

L,CSF)

Bea0ng revs. by PFI mill



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Figure 2. Cross-section of a coir fiber [18].

Figure 3. Beating effect of a coir fiber.



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Paper Properties 1. Basis weight and thickness Beating influenced the basis weight of unbleached coir soda pulp, basis weight was increased until the maximum basis weight was reached and it was 63.9 g/m2 at 3000 beating revolution. Consequently, basis weight decreased if the pulps were continuously beaten for a longer period. In case of thickness, results were 287.7–304.9 µm. Generally, the beating revolution affected individual fiber that could make fiber shorten, reduce cell wall thickness and more fibrillation when beaten fibers were bonded together. The pulp properties will develop and drop until over-beating level. The Fig. 4 shows the relationship between basis weight and thickness and beating revolution of unbleached coir soda handsheet.

Figure 4. Basis weight and thickness vs beating levels of coir soda handsheet.

2. Density and bulk Fig.5 illustrates the effects of beating revolution and degrees of refining (freeness) on the density and bulk of unbleached coir soda handsheet. The figure shows that beating induces an increase of the paper density and a decrease of the bulk until the maximum value at 1500 beating revolution. The density of unbleached coir soda handsheet continued to increase from 0.206 to 0.216 g/cm3 at 0 – 1500 revs, and then it decrease from 0.216 to 0.202 g/cm3 at 1500 – 100000 revs. While, the bulk declined from 4.841 to 4.622 cm3/g at 0 – 1500 revs and then it slightly rose from 4.662 to 4.929 cm3/g at 1500 – 10000 revs. Proceed beating pulp much longer will cause the reverse to the density and bulk.

Thickn

es (µ

)

Basis W

eight (g/m

2 )


Basis weight Thickness



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Figure 5. Density and bulk vs beating levels of coir soda handsheet.

4. Mechanical properties of hand sheet

Tensile index and tear index are probably the most used ones for the direct measurement of the paper strength potential. The dry tensile index and wet tensile index of unbleached coir soda handsheet were 15.23–24.85 Nm/g and 1.05-2.38 Nm/g respectively. Fig.6 shows the relationship between tensile index and freeness on wet and dry paper. It can be seen that the trend of tensile strength development after beating of pulp was identical. When freeness decreased, resulting from increasing beating revolution, tensile index also increased until the maximum tensile index was reached at 1500 beating revolution and 870 ml, CFS. Consequently, tensile index decline if the pulps were continuously beaten for 3000 revs and stable for dry tensile index and rise for wet tensile index applies for a longer period. During beating process, tensile strength increased due to improved fiber swelling, fibrillation, flexibility, hydrogen bond and fiber-to-fiber bonding, but excessive beating would result in fiber 870 ml, CFS. Consequently, tensile index decline if the pulps were continuously beaten for 3000 revs and stable for dry tensile index and rise for wet tensile index applies for a longer period. During beating process, tensile strength increased due to improved fiber swelling, fibrillation, flexibility, hydrogen bond and fiber-to-fiber bonding, but excessive beating would result in fiber cutting, thereby leading to a decrease of tensile strength [18]. Tear strength measures a substantially more complex form of stress transmission than tensile strength. Tear is a measure of the energy required to propagate an out-of plane tear failure line over a predetermined distance in a sheet of paper. As with most cellulosic pulps, the tearing index for all the tested pulp samples decreased with increased refining. The characteristic tear-beating curve shown in Fig.7 illustrates that the maximum attainable tear strength occurs at low levels of beating, and thereafter the tear strength decline then rises again after beating 3000 revs.

Bulk (cm

3 /g)

Density

(g/cm

3 )


Density Bulk



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Figure 6. Dry and wet tensile index vs beating levels of coir soda handsheet.

Figure 7. Tear index vs beating levels of coir soda handsheet.

Dry Tensile In

dex (Nm/g)

Dry Tensile In

dex (Nm/g)


Dry tensile index Wet tensile index

Dry Tear In

dex (m

N m

2/g)




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5. Paper formation and surface morphology of hand sheet

As shown in Fig. 8, beating influences considerably the formation of hand sheet. Relative Formation Values (RFV) more than 1 means that the formation better upon beating. Fig. 9 shows, hand sheets having short and tiny fibers had small gaps between the fibers, for instance fibers in beating 1500 to 10000 revs. As may be noted in pictures, due to the beating process, the pulp produced tiny fibers.

Figure 8. Formation of handsheet with different beating revolutions



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Figure 9. Surface morphology of handsheet different beating revolutions: A. 0 revs; B. 750

revs; C.1500 revs; D. 3000 revs; E. 10000 revs

ACKNOWLEDGMENT The authors would like to acknowledge the support of the DIKTI Research Programs of Indonesia, especially Hibah Disertasi project (023.04.2.415278/2013).

References

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[3] Joedodibroto, R., Beberapa Prospek dan Masalah dalam Pemanfaatan Sabut Kelapa untuk Pulp Kertas, Berita Selulosa, 1, XXVI, 1990, pp. 3-8. [4] Page, D.H., “The beating of chemical pulp-The action and the effects,” in Papermaking Raw materials: Transactions of the Ninth Fundamental Research Symp. Vol 1. Baker C.F and Punton, V.W. (eds.), Mechanical Engineering Publications Ltd. London, UK, 137, 1989. [5] Ebeling, K., “A Critical review of correct theories for the refining of chemical pulp,” International Symposium on Fundamental Concepts of Refining, Institute of Paper Chemistry, Appleton, USA, 1980, pp. 1-36. [6] Ogbonnaya, C.I., Roy-Macauley, H., Nwalozie, M.C., and Annerose, D.J.M., Physical and Histochemical Properties of Kenaf (Hibiscus cannabinus L.) Ground under Water deficit on Sandy Soil, Ind. Crops Prod., 7, 1997, pp. 9-18. [7] Sridach, W., Pulping and paper properties of Palmyra palm fruit fiberss, Songklanakarin J. Sci. Technol., 32, 2, 2010, pp. 201-205. [8] Ogunsile, B.O and Uwajeh, C.F., Evaluation of the pulp and paper potentials of a Nigerian grown Bambusa vulgaris, World App. Sci. J., 6, 4, 2009, pp. 536-541. [9] Agopyan, V., Savastano Jr, H., John, V. M., and Cincotto, M. A., Developments on Vegetable Fibre-cement Based Materials in San Paulo, Brazil: An overview, Cem. Concr. Compos., 27(5) , 2005, pp. 527-536. [10] Law, K., and Jiang, X., ”Comparative papermaking properties of oil-palm empty fruit bunch,” Tappi Journal 84(1), 2001. [11] Khakifirooz, A., Ravanbaksh, F., Samanriha, A., and Kiaei, M., “Investigating the possibility of chemi-mechanical pulping of bagasse,” BioResources 81(1), 2013, pp. 21-30. [12] Salehi, K., “ Study and determine the properties of chemi-mechanical pulping high yields from bagassee,” Wood and Paper Research No. 232, Research Institute of Forests and Rangelands, 2001. [13] Xu F, Zhong XC, Sun RC, Lu Q, Anatomy, ultra structure, and lignin distribution in cell wall of Caragana Korshinskii. Ind. Crops Prod., 24: 186-193, 2006. [14] Istas J.R., Heremans R., Roekelboom, E.L., “Caracteres Generaux De Bois Feuillus Du Congo Belge En Relation Avec Leur Utilization Dans I ‘industrie Des Pates A Papier: Etude Detaillee De Quelques Essences. Gembloux: INEAC (Serie Technique, No. 43), 1954. [15] Bektas, I., Tutus A, Eroglu, H., “A study of the suitability of Calabrian pine (Pinus Brutiaten) for pulp and paper manufacture,” Turkey Journal Agriculture Forest (23), 1999, pp. 589-599. [16] Akkayan SC, Researches on cellulose mixtures obtained from pinus sylvestris (p. sylvestris), Pinus brutia (P. brutia) and Oriental Beech (F. orientalis), Populus euroamericana (P. euroamericana I- 214), Eucalyptus (E. camaldulensis) wood, their properties and their usage possibilities in paper industry. Istanbul Univ. For Faculty PubliSer A, 33: 104-132, 1983. [17] Bostanci S, Chemical components of Turkey picea orientalis and possibilities of using mechanical wood pulp obtained from turkey Picea orientalis and normaniana chips. Ph.D Thesis, Karadeniz Technical University, 1976.



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