Extraction and Characterization of Fiber from the Stem of Cyperus Papyrus Plant

ABSTRACT Owing to environmental concerns caused by the use of synthetic fibers, there is an urgent need to find new eco-friendly fibers. In addition, conventional cellulosic fibers are becoming costly due to an increase in production cost, therefore, sustainable alternative sources of eco-friendly fibers need to be explored. This study investigates the extraction and characterization of fibers from the Cyperus papyrus plant and evaluates its potential as textile fibers. Cyperus papyrus plant fibers were extracted using water retting and alkaline extraction methods and their mechanical, physical, thermal, and chemical properties were studied. The fiber’s chemical composition was established and alkaline extracted fibers contained 61.82% cellulose, 11.82% hemicellulose, 23.6% lignin, 3.86% ash, and 2.75% extractive while the water-retted fibers contained 57.98% cellulose, 13.45% hemicellulose, 25.42% lignin, 6.07% ash, and 3.15% extractive. The fineness of the extracted fibers was 8.38 and 7.31 Tex for water-retted and for alkaline extracted fibers, respectively. The average tensile strength of the extracted fibers ranged from 26.25 to 31.05cN/Tex. The average elongation of the fibers was between 2.02% and 2.79% while its thermal degradation temperature was as high as 150ºC. Compared with conventional fibers, the extracted fibers have the potential of replacing them based on the properties studied.


Introduction
The fibers used in textile manufacturing can be classified into two main groups based on their origin, which can be natural or man-made fibers. Natural fibers have attracted great interest from many scholars because of their abundance, renewability, low cost, eco-friendliness, and CONTACT Rotich K. Gideon rotichgideon@yahoo.com Fiber science, Ethiopian Institute of Fashion and Textile Technology, Bahir Dar University, Ethiopia and weighed for fiber yield calculation. The chemicals used were of analytical grade and were used without alteration.

Chemical extraction
The dried stems were thoroughly washed with distilled water and treated with different concentrations of sodium hydroxide (NaOH) and a variety of liquor ratios as shown in Figure 2 for process optimization. In addition, temperature and time of extraction were also controlled based on the NaOH concentration and the liquor ratio. The optimized condition for extraction of Cyperus papyrus fibers was 3% sodium hydroxide, 30 min, 45ºC temperature, and a material-to-liquor ratio of 1:20.

Water extraction
The prepared sample was immersed in a container of water at room temperature in an open system with different extraction duration and water types. Water retting is a natural occurrence where lignin in the papyrus stem is dissolved using organisms thus releasing the fiber bundles enabling them to be separated into fibers. Figure 3 shows the extraction process of CPFs by the water retting process. The number of experimental runs was determined using the Design Expert software, especially by the response surface optimal (custom) method. Factors needed for the extraction of Cyperus Papyrus fibers by water retting were the duration of extraction (10-40 days) and the water type (treated tap water and river water). After extraction, the fibers from both methods were cleaned thoroughly and dried at ambient conditions before analysis. The fiber yield (%) was calculated using the percentage ratio between the final mass of the fibers before and after extraction process, which is given by Equation (1) (Chakma, Cicek, and Rahman 2017;Indran, Edwin Raj, and Sreenivasan 2014).
where W o is the weight of the dried plant before extraction and W 1 is the weight of fiber after extraction.

Tensile strength and elongation
The tensile strength properties were determined using the Tinius Olsen H1KS single-fiber strength tester as per the ES ISO 5079:2020 standard, equipped with a load cell of 30 kN, at a crosshead speed of 10 mm/min, maintaining a gauge length of 80 mm. Ten samples were tested in each case and an average of the tensile properties was reported.

The density of CPFs determination
The Pycnometer setup is the standard protocol used to assess the density of the natural fibers employing the mass difference technique (Amiri et al. 2017). Liquid acetone of known density was used to perform the density analysis (ρ acetone = 0.7845 g/cm 3 at room temperature). The fibers were cut into small lengths and inserted into the Pycnometer. The mass of the Pycnometer was noted before (m 1 ) and after (m 2 ) filled up with the CPFs. A certain amount of acetone whose mass value (m 3 ) already noted was added to the CPFs. The final mass reading, i.e., the mass of the mixed CPFs with acetone was measured (m 4 ) and noted. Then, the density of CPFs was calculated using Equation (2). This test was performed five times and the average of each noted as the density of Cyperus Papyrus fibers.
Fiber diameter measurement Image analyzer Optical Microscope was used to measure the diameter of the single fibers. For both extraction methods, 15 samples were taken and, in each sample, five random points along the fiber length were measured. Finally, an average diameter of the single fiber was calculated (Nadlene et al. 2015).

Moisture regains and moisture contents
The conventional weight loss method was used to find the amount of moisture content and regain of the CPFs fiber according to the ASTM 2654 test standard (Porras, Maranon, and Ashcroft 2015). The samples were weighed outside the oven and dried in an oven at 105 ± 3ºC until a constant weight was achieved. A total of five samples were tested to get an accurate result and calculated using Equation (

Linear Density Measurement
Linear density (Tex) was determined according to ASTM D 1577-07 standard test method. It was completed using the single-fiber counting and weighing method. For this study, the linear density of CPFs was achieved by taking 15 samples and the length of a single fiber was measured, weighed, and finally, the linear density value in Tex was calculated using Equation (5)

Chemical composition determination
The chemical composition of Cyperus papyrus fibers was determined using standard isolation methods for major fibers' chemical components. Organic (cellulose, lignin, hemicellulose, solvent extractives, and moisture) and inorganic compounds (ash) were determined according to the Technical Association of the Pulp and Paper Industry (TAPPI) standards and calculated using Equation (6) (Plazonić, Barbarić-Mikočević, and Antonović 2016).
where W f and W o are the weights' (g) of the fiber samples before and after treatments. For the determination of extractives, 2 g of dried raw CPFs were placed in a flask with acetone (150 ml) as a solvent and kept for 4 h. After the extraction process, the fiber mass was dried at a temperature of 105 ºC for 30 min. The percentage of extractives was evaluated using Equation (7) (Adeeyo, Oresegun, and Oladimeji 2015).
Two grams of extractive-free CPFs were placed in a flask with 300 ml NaOH solution (20 g/L). Then, the mixture was boiled for 3.5 h with recycled distilled water. After which the residue was washed with distilled water and dried to a constant weight at 105 ºC in an oven (Kale, Taye, and Chaudhary 2019). Finally using Equation (6), the percentage of hemicellulose was calculated.
For lignin determination, 2 g of dried extractives free CPFs were used. Then, the sample was mixed with 60 ml 72% (v/v) sulfuric acid and the solution kept for 2 h at room temperature. Then, the solution was diluted with 600 ml of distilled water and boiled for 1 h. After cooling and filtration, the residue was washed with distilled water, filtered and dried to a constant weight (Amie et al. 2008). The mass percent of lignin was calculated using Equation (7).
Lignin % ð Þ ¼ Mass of the sample after treatment Initial mass of extractive free fiber � 100 (7) The mass percent of cellulose was calculated from the difference of 100 to other components using Equation (8).
The ash content was determined according to the standard procedure TAPPI 211 om-07. The sample was oven dried (105 ± 3°C) to constant weight followed by carbonization over a Bunsen burner and ignition in a muffle furnace at 525°C until ash was completely formed. Finally, the ash content was calculated using Equation (9).

Fourier transform-infrared spectroscopy (FTIR)
FTIR spectrometer was used to determine the presence of functional groups on CPFs. IR spectra of the samples was recorded using the Perkin Elmer FTIR instrument in the frequency range 400-4000 cm −1 using the transmittance mode as a function of wavenumber. First, the fibers were grounded and KBr added followed by pressing the combination into a disk to capture the spectra.

Thermo gravimetric analysis (TGA)
The PerkinElmer TGA 4000 was used to study the thermal stability, mass loss, and transformation of CPFs with respect to heat. The measurement was performed in a nitrogen atmosphere at a flow rate of 20 ml/min, and the mass loss was recorded at a heating rate of 10°C/min with a temperature range of 30−700°C.

Tensile strength properties of CPFs
The average tensile strength of CPFs was 31.05cN/Tex for alkaline extracted fibers and 26.25cN/Tex for water-retted fibers. The increase in the fiber tensile strength of alkaline extracted fibers may be due to the improvement of crystalline index of the fiber due to the removal of hemicelluloses, lignin and pectin during alkali extraction process (Singh et al. 2022). This removal will increase the cellulose proportion, which in turn improves tensile strength. The mechanical properties of fibers majorly depend on the cell wall structure and the chemical composition, especially the cellulose percentage present in the fiber (Prithiviraj et al. 2016). Based on their strength, the possible area of application is the manufacture of composite and paper production. The tensile properties of CPFs are summarized in Table 2 and they have been compared with conventional natural fibers. From the table, it can be seen that the strength, elongation, and density of the extracted fibers compare favorably with other conventional textile fibers hence can be used as a substitute for the same.

The density of CPFs
The density of fibers affects different properties including tensile strength, elongation, and flexibility. Accordingly, based on the principle used in the methodology, the density of CPFs obtained was 0.95 g/ cm 3 for water-retted fibers and 1.15 g/cm 3 for alkali extracted fibers which were comparable with conventional fibers as shown in Table 2. Bio-centered products manufactured using low-density constituents turn out to be of low weight, which is a valuable characteristic in addition to their ecofriendly nature.

Diameter of CPFs analysis
The morphology of single CPFs was observed using an optical microscope and the diameter of the fibers was measured in micrometers. After evaluating at least 15 samples, the average value was obtained as 22.32 ± 0.5 µm for alkaline extracted fibers and 32.37 ± 0.81 µm for water-retted fibers. From this result, it can be observed that during alkaline extraction, removal of non-fibrous parts was more efficient than water retting and the fibers generally had an almost uniform diameter. The same phenomenon was reported by Singh and coworkers when they treated corn fibers with alkaline (Singh et al. 2022). Figure 4 shows the microscopic view of diameter measurement for both water-retted and  (Satyanarayana et al. 1990) alkaline extracted fibers at 100× magnification. From Figure 4, it can be seen that the fibers are made up of parallel micro-fibers bunch up together with the help of gluing power of lignin. As observed, the CPFs is made up of numerous cellulose fibrils attached to one another creating a tightly packed fiber bundle. Fibers were perceived as long and of even cross-section exhibiting a good aspect ratio .

Moisture regains and moisture contents
Most natural fibers tend to absorb moisture when exposed to the atmosphere due to the presence of water-loving groups on their surface. The amount of water absorbed by the textile fiber will depend on the chemical and physical structure plus the fiber properties as well as the temperature and humidity of the surroundings. The percentage absorption of water vapor by a fiber is often expressed as its moisture regain and content as illustrated in Table 3 for the extracted CPFs. From Table 3, the two extracted fibers had almost the same moisture content and regain. The CPFs have good moisture absorption showing that the fibers can be used for applications not exposed to high moisture. Natural fibers are inherently hydrophilic and tend to draw moisture from the environment. This is a limitation from the composite reinforcement point of view because it affects the interfacial adhesion between the fiber and the hydrophobic matrix (Jeyabalaji et al. 2021).

Linear density
The linear density of CPFs is affected by different factors including weighing and measuring, fiber maturity, growing environment, and extraction condition. Fiber fineness affects the material's surface area, porosity, and strength indirectly determining the performance and applications of the fiber. The fineness of CPFs was measured by single fiber principles, which measures the length and mass of a single fiber. Then based on the fiber count formula, the linear density of the fiber is calculated in Tex unit. The mean value of the extracted fiber fineness was 8.38 ± 0.6 Tex for water-retted fibers and 7.31 ± 0.4 Tex for alkali extracted fibers. There was a difference between alkaline extracted fibers and waterretted fibers. The main reason is that in alkali extraction, there was effective removal of lignin making the fibers have a high probability to be separated into finer fibers and its fineness is less than that of water-retted fibers.

Chemical composition analysis
The chemical composition of natural plant fibers varies from one plant to another and from different parts of the same plant. It depends on several factors including plant species, age, climatic conditions, soil composition, and the method of extraction. All plant fibers are composed mainly of cellulose, hemicelluloses, lignin, pectin, and waxes. The analysis of the chemical composition of Cyperus papyrus fiber was established in terms of the amount of cellulose, lignin, hemicellulose, extractive, and ashes, using the standard TAPPI methods, as listed in Table 4 compared with other cellulosic fibers. Table 4 shows that the chemical composition of CPFs is comparable with other conventional fibers indicating that the extracted fibers can be used as an alternative.
The alkali extraction resulted in substantial elimination of lignin and a matching increase in cellulosic proportion. Cellulose is the key structural constituent that gives strength to the fiber. On the other hand, lignin, an extremely net-worked molecular complex, acts as a gluing component among single fiber cells and the fibrils forming the cell wall (Mohanty, Misra, and Hinrichsen 2000).

Fourier transform-infrared analysis
Generally, natural plant fibers are lignocellulosic substrates that have a heterogeneous structure and show a spectral pattern with relatively pointed absorption bands. Fourier-transform infrared spectroscopy was used to characterize the extracted fibers, using the infrared characteristics transmittance bands of their constituents (Mayandi et al. 2015). The FTIR spectra of the CPFs are shown in Figure 5. It can be seen that the spectrum exhibits peaks from 3334 to 472 cm −1 as other natural fibers . The same observations were made by Bemerw and coworkers in their work with Papyrus Fibers (Bemerw et al. 2021) The peak at 3334 and 3321 cm −1 refers to O -H stretching due to the presence of cellulose. The peak at 2926, 2922, and 2851 cm −1 represent the C -H stretching, which occurs due to the vibration of cellulose and hemicellulose (Santhanam et al. 2016). The bands emerging at 1602, 1453, and 1377 cm −1 were assigned to stretching of the benzene ring, CH 2 deformation, and CH 3 bending attributed to bending vibration of C-H and C-O groups of the aromatic ring of hemicellulose and lignin, respectively. The 1243 cm −1 band denotes C-O stretching vibration of acetyl groups in lignin while 1037 cm −1 band denotes alkoxy C-O ordinary bond bending vibration and the minor peak at 837 cm −1 designates C-O stretching and ring vibrational modes. The high peak at 546 cm −1 denotes C-OH out of plane bending motion .

Thermo gravimetric analysis
It is essential to identify the thermal performance of fiber in advance in order to determine its suitability for high-temperature applications (Ramkumar and Saravanan 2021). The nature of the TGA curves indicates the stages of thermal degradation, which is related to the chemical composition. Figure 6 shows the weight loss with respect to temperature curves of alkaline and water extracted Cyperus Papyrus fibers. According to various studies, these curves reflect different decomposition steps that are directly related to the disintegration of the fiber main components (Marcilla et al. 2009). TGA continuously weighs a sample to the smallest gram as it is being heated to a temperature up to 700°C. As the temperature increases, the various components of the sample degrades, and the weight % of each can be measured. Results are in the form of a graph with temperature plotted on the x-axis and weight percentage plotted on the y-axis. It is evident from Figure 6 that the TGA curve of the CPFs shows similarity to other natural fibers as it decreases its mass in three separate stages. The first stage corresponds to a CPFs drying phase during which moisture and volatile compounds are eliminated at temperatures ranging from room temperature to 130°C and 167°C for both water and alkaline extracted fibers, respectively. The weight loss is due to the evaporation of water molecules existing in the raw fiber attributable to its hydrophilic nature. Polymer decomposition is indicated by a large weight loss beginning at 130°C at which the hemicellulose component began to break down. The rate of weight loss rapidly increased at temperatures above 130°C (Liu et al. 2002).
The active pyrolysis process occurred between the temperatures of 130°C and 400°C. In this region, the degradation of the hemicellulose and cellulose portion of the CPFs occurred. Cellulose needs a higher temperature compared to hemicellulose to decompose because of its long-chain structure. The maximum rate of degradation occurred at temperatures of 130-265°C for hemicellulose and 265-400°C for cellulose. In this region, the rate of weight loss increased rapidly. Figure 7 indicates that the decomposition temperature of hemicellulose as 245.56°C and for cellulose as 383.3°C. The disintegration of cellulose goes hand in hand with the degradation of lignin that may have been initiated at a lower temperature and linger up to 400°C. The breakdown of glycosidic bonds in the fibers occurs in the temperature range of 265-400°C (Radhaboy et al. 2022).
The final stage of pyrolysis occurred between the temperatures of 400-700°C. At this temperature range, passive pyrolysis occurs, in which degradation of the most complex structure of CPFs takes place, and in this case, minor weight loss occurred.

Conclusion
The new natural lignocellulosic fibers were successfully extracted from the Cyperus papyrus plant using water retting and alkaline extraction methods. The non-fibrous components were effectively removed in both extraction methods with optimized conditions without affecting the properties of the fibers. The optimized conditions for extraction of Cyperus papyrus fibers were 3% sodium hydroxide, 30 min, 45 ºC temperature at a material to liquor ratio of 1:20 for alkaline extraction, while waterretting needed 34 days using tap water. The extracted fibers exhibit satisfactory mechanical properties, good moisture regain, and low density. The tensile strength and elongation were found to be between 26.25 and 31.05 CN/tex and 2.02-2.79% for water-retted and alkaline extracted fibers, respectively. It also had average moisture regain of 11.02% and moisture content of 9.9%. This fiber has a linear density of 8.38 Tex for water-retted and 7.31 Tex for alkaline extracted fibers. The chemical composition of the CPFs was found to be 61.82% cellulose, 11.82% hemicellulose, 23.6% lignin, 3.86% ash, and 2.75% extractive for alkaline extraction and be 57.98% cellulose, 13.45% hemicellulose, 25.42% lignin, 6.07% ash, and 3.15% extractive for water extraction. This proves that the extracted fibers have a comparable chemical composition with other conventional natural fibers like Napier grass, Coir, Althaea, Bamboo, and Kenaf. The FTIR curves of both water and alkaline extraction showed the presence of functional groups of cellulose, hemicellulose, and lignin. The thermal analysis of CPFs showed that the CPFs had a resistance to temperature up to 150ºC and degradation occurred at a temperature of 245.56ºC for hemicellulose and at 383.3ºC for cellulose components of the fibers. From the results, the papyrus fibers properties are comparable with already established fibers. Therefore, the fiber can serve as an alternative for the existing fibers in textile applications especially composite reinforcement. The future work include the development of composites reinforced with papyrus fibers and characterizing them for their mechanical properties.
• The FTIR curves show the presence of functional groups of cellulose, hemicellulose, and lignin.
• The thermal analysis of CPFs showed that the CPFs had resistance to temperatures up to 150ºC and decomposition occurred at a temperature of 245.56ºC for hemicellulose and at 383.3ºC for cellulose components of the fibers. • Compared with conventional fibers, the extracted fibers have the potential of replacing them for composite reinforcement based on the properties studied.

Disclosure statement
No potential conflict of interest was reported by the author(s).

Funding
This work was supported by the Postgraduate office, Ethiopian Institute of Textile and Fashion Technology, Bahir Dar University, Ethiopia.