Research Article

Relationship Between Fiber Characteristics and Pulping Properties of Ipil Ipil (Leucaena leucocephala) Tree Grown in Khyber Pakhtunkhwa

Muhammad Umair Khan*, Zahid Rauf, Abdur Rehman, Tanvir Hussain and Mansoor Ali Khan

Pakistan Forest Institute, Peshawar, Khyber Pakhtunkhwa, Pakistan.

Received | April 05, 2023; Accepted | May 03, 2023; Published |June 26, 2023

*Correspondence | Muhammad Umair Khan, Pakistan Forest Institute, Peshawar, Khyber Pakhtunkhwa, Pakistan; Email: [email protected]

Citation | Khan, M.U., Rauf, Z., Rehman, A., Hussain, T. and Khan, M.A., 2023. Relationship between fiber characteristics and pulping properties of ipil ipil (Leucaena leucocephala) tree grown in Khyber Pakhtunkhwa. Pakistan Journal of Forestry, 73(1): 17-23.

DOI | https://dx.doi.org/10.17582/journal.PJF/2023/73.1.17.23

Keywords | Fiber dimensions, Pulping properties, Relationship, Ipil ipil (Leucaena leucocephala)

Copyright: 2023 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Manufacturing of pulp and paper products is one of the valuable and oldest practice. Paper is a social and educational product and plays an important role in the daily life of people in numerous shapes from packaging to high-quality paper. The primary uses of paper products are in office handlings, cardboard, packaging material, books, magazines and newspaper etc. The world demands for more paper products by coming years, and consequently arises the number of paper industries in the world. To produce and satisfy the demand for paper worldwide, these industries require raw materials. Paper products are manufactured from various raw materials including wood, recycled papers and non-wood materials (Kaur et al., 2017; Przybysz and Buzała, 2014).

The continuous development in Pakistan has led to a rapid increase in the country’s demand for paper products. The majority of developing countries including Pakistan depends almost entirely on imports to meet its demand of pulp and paper even though the country is rich in various hardwood species that might serve as good source for pulp and paper production. The original properties of fiber and its outcomes from the processing variables determine successful transformation of pulp into a marketable product. The original fiber properties and the fiber’s response to processing variables are both important factors in the production of paper sheets and their physical characteristics. Since there is an enormous range of wood species, even though processing conditions may have been the same, the physical characteristics of a piece of paper from one species will frequently differ considerably from a similar piece from another species. In order to evaluate the pulp quality of fiber, it is necessary to analyze fiber properties such as fiber length, fiber diameter, lumen width, cell-wall thickness, and the morphological features that result from these pulps (Amidon, 1981; Dinwoodie, 1965; Wood, 1981). Fiber length was the first property of fiber related to its strength properties. It has been evaluated by several researchers that bonding sites extensibility depend on fiber length (Horn, 1974).

In the nutshell, due to the longer fiber length of softwood pulps leads to greater paper strength as compared to the shorter fiber length of hardwood. The strength and rigidity of the paper made from the fiber also depends on other anatomical parameters like cell wall thickness and lumen size (Panshin and De Zeeuw, 1964). Thin walled and large lumen fibers show good strength characteristics due to strong flattening inter-fiber bonding (Oluwadare, 1998).

As experts predicted the crises of wood fibers for the forthcoming supply of fiber due to the high demand of paper products worldwide, it become necessary for pulp and paper production to throw light on lesser used species of wood. Leucaena leucocephala belongs to this category. For paper manufacturing, Leucaena is one of the best tropical hardwood evaluated by its chemical analysis and fiber (Oluwadare and Sotannde, 2007). The present study analyzes and investigates the mutual relationship of pulping properties and fiber characteristics of Leucaena leucocephala grown in Khyber Pakhtunkhwa, Pakistan, in an effort to forecast pulp sheet performance depending on the fiber content and Kraft pulp quality.

Materials and Methods

Wood material of Ipil ipil (Leucaena leucocephala) was purchased across the province of Khyber Pakhtunkhwa. The morphological characteristics of fiber has an important role in finding the suitability of a wood species for pulp and paper manufacturing which were studied in Wood Anatomy laboratory, Pakistan Forest Institute (PFI), Peshawar. Pulping characteristics of the collected wood species were studied in Pulp and Paper laboratory, PFI. Further, pulp and paper preparation from Leucaena leucocephala; testing and evaluation of its sample papers for various strength were also carried out in Pulp and Paper laboratory.

Fiber analysis

In order to study the fiber morphological characteristics of the collected wood species, a small amount of wood was macerated in Schulze’s combination (20% nitric acid and potassium chlorate) for separation of fibers. Then after thorough washing, the fibers were stained in Safranin stain and observed under microscope (Nikkon 55 I Eclips) to measure fiber dimensions. The mean fiber characteristics with their derived morphologies of Ipil ipil (Leucaena leucocephala) are shown in Table 1.

Based upon the presented fiber morphological characteristics of Ipil ipil (Leucaena leucocephala) in Table 1, the calculated wood properties of Ipil ipil (Leucaena leucocephala) wood are hereby calculated and shown in Table 2.

 

Table 1: Fiber morphological characteristics of Ipil ipil (Leucaena leucocephala) wood.

S. No	Fiber Characteristics	Samples						Standard deviation	Co-efficient of variation
		S1	S2	S3	S4	S5	Average value
1	Fiber length (mm)	0.92	0.88	1.1	1.41	1.42	1.15	0.27	23.47
2	Fiber diameter (microns)	18.42	17.81	23.1	29.51	28.99	23.66	5.85	24.75
3	Fiber wall thickness (microns)	2.67	3.11	2.95	2.69	4.59	3.63	0.96	26.52
4	Fiber lumen width (microns)	13.87	16.8	15.01	18.79	17.25	16.34	2.45	14.99

 

Table 2: Arithmetic ratios/ calculated wood properties of ipil ipil (Leucaena leucocephala) wood.

S.	Property	Value
1	Runkel ratio (2 x fiber call wall thickness/lumen width)	0.44
2	Flexibility ratio (fiber lumen width/ fiber diameter)	0.69
3	Felting power ratio (fiber length/ fiber diameter)	43.81
4	Rigidity coefficient (fiber wall thickness/fiber diameter)	0.15

 

Pulping experiment

The logs of the purchased wood species were debarked and disintegrated into chips using Staffi Chipper. Chips prepared from Ipil ipil wood species were classified and N-3 fraction (1 inch in length and 3.2 mm in thickness) were used for pulp manufacturing. The wood chips were pulped using Kraft method. The chips were dried and cooked at 15% alkali and 25% Sulphidity at 170 oC for 3 hours in the pulp digester. The digested pulp was disintegrated to get uniform pulp and percent yield was calculated and beaten for fiber freeness through SR (Schopper Regiler) beater. The cooking parameters are shown below.

Handsheet preparation and testing

The dried Ipil ipil from the experiment was used for the sheet preparation procedure. A laboratory valley beater was used to beat the pulp as per TAPPI standards (TAPPI, 1999). Paper handsheets of pulp sample were prepared using a standard handsheet former as described in TAPPI test T205 sp-02. Each of the handsheet made at three level of freeness was put to the tests of grammage, density, density, bulk, roughness, porosity and tear resistance according to TAPPI standards (TAPPI, 2000).

 

Chips weight	1070 g
Na2S	50 g
NaOH	150 g
Active alkali	15%
Sulphidity	25%
Cooking time	3 hours
Cooking temperature	170 oC
Wood : Liquid	1:5
Cooking yield	44.4%

 

Papermaking properties

Paper sheets have certain primary papermaking properties for determination of paper quality such as density, bulk, roughness, porosity and tear strength etc. Pulps from Ipil ipil sample were beaten in a Schopper Regiler to three different level of freeness (oSR). The paper sheets prepared from the Ipil ipil wood specie were tested for the evaluation of physic-mechanical properties according to standards (TAPPI, 2000). Five different samples of pulp sheet prepared from Leucaena leucocephala wood were tested for physico-mechanical properties of the sheet at Pulp and paper laboratory. The results are presented in Table 3.

 

Table 3: Pulp-sheet properties of Kraft pulp of Leucaena leucocephala wood at different freeness levels.

S. No	Pulping property	Freeness (oSR) 25							Standard deviation	Coefficient of variation
		S1	S2	S3	S4	S5		Average value
1	Grammage (g)	56.7	63	59.85	69.3	66.15		63	4.98	7.91
2	Density (g/cm3)	1.22	1.29	1.5	1.43	1.36		1.36	0.11	8.14
3	Bulk (cm3/g)	0.7	0.66	0.73	0.77	0.8		0.73	0.06	7.59
4	Roughness (ml/min)	564	595	659	627	690		627	49.96	7.97
5	Porosity (ml/min)	2846	3478	3004	3320	3162		3162	249.82	7.90
6	Tear Resistance (mN)	49	47	52	57	55		52	4.12	7.93
		Freeness (oSR) 43
1	Grammage (g)	61.75	65	58.5	68.25	71.5	65		5.14	7.91
2	Density (g/cm3)	1.38	1.46	1.61	1.68	1.53	1.53		0.12	7.75
3	Bulk (cm3/g)	0.71	0.68	0.59	0.62	0.65	0.65		0.05	7.30
4	Roughness (ml/min)	550	572	618	595	640	595		35.74	6.01
5	Porosity (ml/min)	2781	2642	2503	3059	2920	2781		219.78	7.90
6	Tear Resistance (mN)	45	47	55	53	50	50		4.12	8.25
		Freeness (oSR) 67
1	Grammage (g)	69.3	63	59.85	56.7	66.15	63		4.98	7.91
2	Density (g/cm3)	1.6	1.69	1.78	1.96	1.887	1.78		0.15	8.16
3	Bulk (cm3/g)	0.54	0.51	0.56	0.59	0.61	0.56		0.04	7.08
4	Roughness (ml/min)	409	431	454	499	477	454		35.74	7.87
5	Porosity (ml/min)	1908	1817	1635	1999	1726	1817		143.88	7.92
6	Tear Resistance (mN)	42.71	40.68	38.65	36.62	44.74	40.68		3.21	7.89

 

Statistical analysis

The Relationship between pulp sheet properties at the 3-level of freeness and fiber characteristics were determined using Pearson correlation coefficient.

Results and Discussion

The relationship between paper and fiber must be interpreted with the indication whether softwood or hardwood is utilized for papermaking (Dinwoodie, 1965). Softwoods are more homogenous in their anatomical structure as compared to hardwoods. The heterogeneity of hardwoods make them complicated to analyze the morphology of fiber and their impact on the characteristics of hardwood-based papers. The relationship that was found to arise from even the most significant hardwood fiber parameter to a particular paper property was generally found to be less certain than in the case of softwood fibers (Horn, 1974). However statistical study of correlation between paper and fiber can provide a wide understanding of suitability of hardwood as a potential raw material in the production of pulp and paper.

Pearson correlation coefficients among fiber diameter, fiber length, fiber lumen width and fiber wall thickness of Ipil ipil wood fibers; and the grammage, density, bulk, roughness, porosity and tear resistance of the Ipil ipil wood paper sheet were calculated to evaluate the relationship between these parameters.

The morphological characteristics of Ipil ipil (Leucaena leucocephala) are shown Table 1. The mean fiber diameter, fiber length, fiber lumen width and fiber wall thickness were 23.66µm, 1.15mm, 16.34µm and 3.63µm respectively. While Runkel ratio, flexibility ratio, felting power ratio and rigidity coefficient were 0.44, 0.69, 43.81 and 0.15 respectively as shown in Table 2. Similarly, properties of Pulp-sheet of Kraft Leucaena leucocephala pulp at three levels freeness were presented in Table 3. The detailed correlations between morphological characteristics and pulping properties at three different freeness level (oSR) are shown in Table 4.

The properties of finished products for papermaking are determined by characteristics of pulp fibers and their processing parameters. Morphological characteristics of fiber play an important role to evaluate a raw material suitability for pulp and paper production. The fiber properties of Ipil ipil are listed and recorded in Table 1. The fiber length was observed to vary between the five different samples of Leucaena leucocephala. The length of Leucaena leucocephala fibers ranged from 0.88 to 1.42 mm, which is acceptable for hardwood (0.7 to 3.0 mm) fiber length and less than that of softwood (2.7 to 4.6 mm) fibers (Mousavi et al., 2013). The mean fiber length of Ipil ipil fiber species projected in this study is in acceptable range for paper and pulp production from hardwood.

The analysis of this investigation shows that tear resistance of sheets made from Leucaena leucocephala fibers principally dependent upon fiber length and fiber diameter (Table 4). However, it shows a slight negative correlation with these two factors at Freeness level (oSR) 67 as r= -0.1 and r= -0.16, respectively. In contrast, fiber wall thickness and lumen width are significant factors in paper made from softwood (Horn, 1974). Along with fiber length and fiber diameter, the tear resistance shows, too, a significant relation to fiber wall thickness and fiber lumen width. The fiber cell wall attributes significantly to the solid mass of fiber. Fiber lumen is referred to the central cavity in the fiber, which is vacate. Lumen width and fiber wall thickness are important variables for

 

Table 4: Relationship between pulping properties and fiber characteristics of Leucaena leucocephala.

	Freeness level (oSR) 25					Freeness level (oSR) 43					Freeness level (oSR) 67
	FL	FD	FWT	FLW		FL	FD	FWT	FLW		FL	FD	FWT	FLW
Grammage	0.79	0.80	0.33	0.99		0.69	0.65	0.65	0.77		-0.40	-0.46	0.32	-0.62
Density	0.54	0.60	0.03	0.35		0.72	0.77	-0.03	0.65		0.94	0.96	0.35	0.84
Bulk	0.96	0.95	0.56	0.48		-0.54	-0.60	-0.03	-0.35		0.96	0.95	0.55	0.48
Roughness	0.74	0.75	0.73	0.40		0.93	0.95	0.31	0.84		0.93	0.95	0.31	0.84
Porosity	0.14	0.15	0.12	0.79		0.71	0.68	0.19	0.66		0.07	0.06	-0.48	0.34
Tear resistance	0.97	0.98	0.28	0.63		0.58	0.64	0.01	0.37		-0.10	-0.16	0.70	-0.35

 

Pearson Correlation coefficient: 1 shows strong positive correlation, -1 shows strong negative correlation. FL: Fiber length, FD: Fiber diameter, FWT: Fiber wall thickness, FLW: Fiber lumen width.

 

pulp refining. Those fibers easily collapse which have thin cell. That is the reason, fiber wall is considered one of the significant factors of fibers affecting paper properties. Dense and well-bonded sheets are produced from pulps made from thin-walled and wide lumen fibers, whereas bulky sheets with good tearing resistance are made from pulps with thick cell wall (Anupam et al., 2016). This correlation analysis showed that a significant percentage of change in the tearing resistance of Ipil ipil pulp could be considered from the aforementioned fiber morphological characteristics.

Further, paper sheet properties, the density and bulk, exhibiting the most by these factors. These paper sheets properties of Leucaena leucocephala fibers are affected mainly by fiber length and fiber diameter (Table 4). After reaching to the freeness level (oSR) of 43, the bulk property showed negative correlation to fiber diameter and fiber length as r= -0.6 and -0.54, respectively. Other properties of paper sheet like grammage, roughness and porosity, made from Leucaena leucocephala were also found to be significant to morphological factors of fibers.

The suitability of the fibrous raw material in the production of pulp and paper might have been assessed using the Runkel ratio, flexibility ratio, felting power ratio and rigidity coefficient determined from fiber dimensions. The suitableness of papermaking has a relationship with the Runkel ratio. A suitable pulp can be made from fibers which have Runkel ratio less than 1.0 (ROH, 1949). A low Runkel ratio fibers are less stiffer consequently make low bulk paper as compared to high Runkel ratio fibers (Ashori and Nourbakhsh, 2009). However, fibers with lower Runkel ratio also make paper with good strength properties due to high collapsibility of fibers (Ishiguri et al., 2016). The mean Runkel ratio in this study from Leucaena leucocephala species were found less than 1.0 (Table 2), indicating that the Ipil ipil species fibers would be capable to produce a paper with good quality properties.

The ratio of fiber lumen width to fiber diameter is known as fiber flexibility. The paper strength can be assessed from flexibility coefficient as flexibility ratio is associated with the fiber potential of collapsibility during paper web drying or beating process. The bonding area between collapsed fibers would be greater which result in production of stronger paper (Ashori and Nourbakhsh, 2009). Moreover, like tear factor and burst factor, flexibility coefficient is also associated positively to strength properties of paper (Moriya, 1967). Many Eucalyptus species had reported values of flexibility coefficient varied between 0.37 and 0.65 (Pirralho et al., 2014) and was found 0.72 and 0.70 in E. globulus and E. camaldulensis respectively (Ona et al., 2001). In the present study, the mean value for the flexibility coefficient of Leucaena leucocephala was 0.69 (Table 2).

The average value of felting power ratio was found 43.81 for Leucaena leucocephala (Table 2). The folding endurance and tearing strength of paper is correlated with the felting power ratio (Ohshima et al., 2005; Yahya et al., 2010). The high value of felting power ratio represents a well-bonded and better formed paper. The felting power ratio in previous studies for many Eucalyptus species were calculated between 39.4 and 48.4 (Pirralho et al., 2014). The felting power values for E. globulus and 14-years old E. camaldulensis ranged 57.7 to 59.9 and 50.5 to 56.5, respectively (Ohshima et al., 2005). The value for the Leucaena leucocephala studied here were similar or slightly lower than these previously reported values.

Conclusions and Recommendations

It had been shown from the result of this work that the strength properties of the pulp sheet of Leucaena leucocephala were significantly influenced by the characteristics and morphologies of the fiber. It seems difficult to predict the quality and performance of pulp on the basis of a single morphological factor. However, Leucaena leucocephala pulp had been influenced greatly by fiber length and fiber diameter. The investigation indicates that Ipil ipil wood has longer, larger in diameter and lumen width and somewhat thick-walled fibers. The wood has acceptable value of Runkel ratio value, higher value of flexibility ratio, medium value of felting power ratio and lower value of rigidity co-efficient ratio. Ipil ipil wood is a good source of fibers and can be used as raw material for paper making with high strength properties due to higher value of grammage and density that contribute to strength of paper and medium for printing purpose as the bulk value is average. It may also produce high tearing resistance, flexible with better fording endurance and bursting strength and medium binding and mating of fibers in paper sheet.

Acknowledgement

I would like to express my sincere gratitude to the Pakistan Forest Institute, Peshawar for their generous provision of resources, expertise, and encouragement, all of which have been instrumental in shaping the direction and outcome of the study.

Novelty Statement

This study explores the relationship between fiber characteristics and pulping properties of Ipil Ipil (Leucaena Leucocephala) trees in Khyber Pakhtunkhwa, Pakistan. Amidst Pakistan’s diverse hardwood resources, this research fills a critical gap by evaluating the untapped potential of locally available raw materials for the pulp and paper industry.

Author’s Contribution

Muhammad Umair Khan: Collected the samples of Ipil ipil tree from different regions of KPK. Prepared the samples for pulp preparation and then manufactured papers from these pulps. Performed and evaluated different physiomechanical tests of paper. Performed the statistical analysis and composed the manuscript.

Zahid Rauf: Assisted and contributed in pulp and paper preparation according to standards, their testing and statistical analysis.

Abdur Rehman: Contributed in sample collection, paper preparation and organizing the data.

Tanvir Hussain: Determined the morphological parameters of fibers of Ipil ipil wood tree.

Mansoor Ali Khan: Prepared various chemical solutions for pulping and performed chemical processes in pulping.

Conflict of interest

The authors have declared no conflict of interest.

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