2.1. Biometric characteristics of G. scortechinii

Table 1 shows the biometric characterization of the studied bamboo (G. scortechinii) species compared with some other natural fibers for pulp and paper making. From the table, it means that the bamboo species under study possesses relatively long fibers, 1980 μm, compared to Eucalyptus (840 μm), B. tulda (1890 μm) and cotton stalks (810 μm).

Many studies have reported that the fiber length of bamboo is generally greater than hardwood and is similar to softwood [14]. Fiber length may actually be a detriment to good strength properties, as in the case of certain non-wood fibers, such as bamboo, bagasse and cotton. In such a case, fibers are longer than 2 μm [15]. The long fibers are covered with fibrils, fines, and the large fibrils effectively serve to bridge the gaps between the naturally rough surfaces of adjacent fibers. In this way, long fibers have an effect on the strength of a bond and especially its toughness, which is characteristic of the bonds between natural paper making fibers and which is completely lacking with bonds between smooth viscose fibers. On the other hand, water drains from long fiber pulps more rapidly, and this is a point in their favor. Therefore, for pulp and paper production, species with higher fiber lengths are preferred since a better fiber net can be achieved, resulting in a paper with high resistance. The biometric characteristic of G. scortechinii shows favorable properties as a fiber raw material for pulp and paper.


FL = fiber length, FD = fiber diameter, LD = lumen diameter, CWT = cell wall thickness, Runkel ratio = (2 CWT)/LD, Flexibility ratio = (LD/FD) 100, Slenderness ratio = (FL/FD).

Table 1. Biometric characteristics of bamboo and other natural fibers.

The average fiber diameter of G. scortechinii is 17.27 μm which is in the range of other species of Bambusa genera. The lumen diameter and cell wall thickness of bamboo was 8.66 μm and 3.74 μm, respectively. The lumen diameter and cell wall thickness influence the beatability of fibers. Fibers with large lumen diameter and thin walls such as in bamboo have higher bonding abilities due to the better penetration by water into the cell wall and into the lumen causing the cells to swell. The combined effects of the beating action and swelling cause the bonds between the structures of lamellas to loosen and easily separate [16].

The lignin content of G. scortechinii is 26%, which is less than the tropical hardwood. Also, G. scortechinii contains about 3.68% solvent extractive which is quite similar to softwood (3%) but is less than solvent extractive reported for hardwood. G. scortechinii has high 1% NaOH solubility (19.82%). 1% NaOH solubility of G. scortechinii shows that more low molecular weight components such as hemicellulose could be solved during the alkaline degradation. As a result, the pulp yield of alkaline pulping of bamboo could be decreased and consumption of alkali charge could be increased due to this property [28, 29]. The hot and cold water solubility of bamboo culms were 5.53 and 4.61%, respectively. Extraction with hot water removes carbohydrate materials such as starches. Extraction with cold water removes sugars, gums, tannins, and inorganic compounds [30]. As it is shown in Table 2 the ash content of G. scortechinii was 1.98%. The ash content of bamboo culms was higher than the aspen and white oak with values of 0.43 and 0.87%, respectively [31]. The silica content of G. scortechinii was 1.56%, which is low compared with non-wood species such as rice (14.9%) and wheat straw (4.35%). Silica results in many problems such as blunting of saw tooth, scaling during chemical recovery of black liquor and covering the outer surface of fiber during cooking. On the other hand, the silica is dissolved in alkali solutions; therefore, the consumption of alkali charge in

Table 2. Comparison of the chemical compositions of bamboo with other natural fibers.

SE = solvent extractives (ethanol-benzene), HWS = hot water solubility, CWS = cold water solubility, and 1% NaOH = 1%

G. scortechinii P. bambusoides Rice straw P. orientalis

Alkaline Sulfite Anthraquinone and Methanol (ASAM) Pulping Process of Tropical Bamboo…

http://dx.doi.org/10.5772/intechopen.76806

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Holocellulose 68.33 3.7 70.50 70.90 74.46 Cellulose 47. 67 3.4 43.30 48.20 44.31 Lignin 26. 00 2.3 24. 50 17.20 25.20 Solvent extraction 3.64 3.2 3.90 3.50 3.40 1% NaOH 19.82 3.5 25.10 49.20 10.26 HWS 5.53 1.2 6.50 16. 20 2. 81 CWS 4. 61 1.4 — 10.70 1.47 Ash 1.98 0.33 1.40 16.60 0.32 Silica 1.56 0.25 — 14.90 — Reference Present study [17] [18] [19]

Traditionally, kraft pulping has been the most commonly reported pulping milieu for bamboo species [33]. This is due to its strong bundle sheathes, impenetrable epidermis, a complete absence of ray cells and limited area of conducting tissues. As good as this pulping technique

cooking liquor is increased [32].

Composition % Natural fibers

sodium hydroxide solubility.

3. Pulping of bamboo (G. scortechinii)

#### 2.2. Chemical compositions

The chemical compositions of G. scortechinii are shown in Table 2. The results showed that the G. scortechinii had high contents of ash and silica (1.98 and 1.56%, respectively), but the results were within the range of tropical hardwood, which is 1–3% [20].

The mechanical properties of final paper are related to the amount of hemicellulose and cellulose contents of raw materials. In addition, polysaccharides such as cellulose and hemicellulose have a positive effect on pulp yield of alkaline pulping process [21]. Raw material with more than 34% of cellulose content can be used for pulp and paper production [22]. The cellulose content of G. scortechinii is in the range of both soft and hardwood, 40–52% and 38– 56%, respectively [23]. The cellulose molecule has numerous hydroxyl groups, which have a strong tendency toward hydrogen bonding with hydroxyl of adjacent molecules [24]. This tendency in connection with the molecular structure is responsible for increasing fiber-to-fiber bonding in final paper [25, 26]. The free hydroxyl groups of cellulose have a strong affinity for polar solvents and solutes that can reach them. An example of this type of interaction is the swelling of cellulose with water. During swelling, the hydrogen bonds between cellulose molecules are broken and replaced by hydrogen bonds between the cellulose molecular and water. Therefore, the cellulose content in the surface of fibers formed with water was a true chemical hydrate and, being glue-like, caused the strength of the resulting paper to increase as well [27].


SE = solvent extractives (ethanol-benzene), HWS = hot water solubility, CWS = cold water solubility, and 1% NaOH = 1% sodium hydroxide solubility.

Table 2. Comparison of the chemical compositions of bamboo with other natural fibers.

The average fiber diameter of G. scortechinii is 17.27 μm which is in the range of other species of Bambusa genera. The lumen diameter and cell wall thickness of bamboo was 8.66 μm and 3.74 μm, respectively. The lumen diameter and cell wall thickness influence the beatability of fibers. Fibers with large lumen diameter and thin walls such as in bamboo have higher bonding abilities due to the better penetration by water into the cell wall and into the lumen causing the cells to swell. The combined effects of the beating action and swelling cause the bonds

FL = fiber length, FD = fiber diameter, LD = lumen diameter, CWT = cell wall thickness, Runkel ratio = (2 CWT)/LD,

FL (μm) 1980 3.3 1890 840 810 19 FD (μm) 17.27 3.7 3.45 10.1 16.75 10 LD (μm) 8.66 2.3 6.78 4.4 4.12 4.5 CWT (μm) 0.86 0.20 3.93 0.87 0.49 0.9 Runkel ratio 50.14 3.6 20.29 53.15 67.05 52.63 Flexibility ratio 114.64 3.6 111.2 44.21 32.42 152.63 Slenderness ratio This study [10] [11] [12] [13]

G. scortechinii Bambusa tulda Eucalyptus grandis Cotton stalk Spruce

The chemical compositions of G. scortechinii are shown in Table 2. The results showed that the G. scortechinii had high contents of ash and silica (1.98 and 1.56%, respectively), but the results

The mechanical properties of final paper are related to the amount of hemicellulose and cellulose contents of raw materials. In addition, polysaccharides such as cellulose and hemicellulose have a positive effect on pulp yield of alkaline pulping process [21]. Raw material with more than 34% of cellulose content can be used for pulp and paper production [22]. The cellulose content of G. scortechinii is in the range of both soft and hardwood, 40–52% and 38– 56%, respectively [23]. The cellulose molecule has numerous hydroxyl groups, which have a strong tendency toward hydrogen bonding with hydroxyl of adjacent molecules [24]. This tendency in connection with the molecular structure is responsible for increasing fiber-to-fiber bonding in final paper [25, 26]. The free hydroxyl groups of cellulose have a strong affinity for polar solvents and solutes that can reach them. An example of this type of interaction is the swelling of cellulose with water. During swelling, the hydrogen bonds between cellulose molecules are broken and replaced by hydrogen bonds between the cellulose molecular and water. Therefore, the cellulose content in the surface of fibers formed with water was a true chemical hydrate and, being glue-like, caused the strength of the resulting paper to increase

between the structures of lamellas to loosen and easily separate [16].

were within the range of tropical hardwood, which is 1–3% [20].

2.2. Chemical compositions

Biometric parameters Type of fibers

12 Bamboo - Current and Future Prospects

Flexibility ratio = (LD/FD) 100, Slenderness ratio = (FL/FD).

Table 1. Biometric characteristics of bamboo and other natural fibers.

as well [27].

The lignin content of G. scortechinii is 26%, which is less than the tropical hardwood. Also, G. scortechinii contains about 3.68% solvent extractive which is quite similar to softwood (3%) but is less than solvent extractive reported for hardwood. G. scortechinii has high 1% NaOH solubility (19.82%). 1% NaOH solubility of G. scortechinii shows that more low molecular weight components such as hemicellulose could be solved during the alkaline degradation. As a result, the pulp yield of alkaline pulping of bamboo could be decreased and consumption of alkali charge could be increased due to this property [28, 29]. The hot and cold water solubility of bamboo culms were 5.53 and 4.61%, respectively. Extraction with hot water removes carbohydrate materials such as starches. Extraction with cold water removes sugars, gums, tannins, and inorganic compounds [30]. As it is shown in Table 2 the ash content of G. scortechinii was 1.98%. The ash content of bamboo culms was higher than the aspen and white oak with values of 0.43 and 0.87%, respectively [31]. The silica content of G. scortechinii was 1.56%, which is low compared with non-wood species such as rice (14.9%) and wheat straw (4.35%). Silica results in many problems such as blunting of saw tooth, scaling during chemical recovery of black liquor and covering the outer surface of fiber during cooking. On the other hand, the silica is dissolved in alkali solutions; therefore, the consumption of alkali charge in cooking liquor is increased [32].
