Study on Extraction of Bamboo Fibres from Raw Bamboo Fibres Bundles Using Different Retting Techniqu

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Textiles and Light Industrial Science and Technology (TLIST) Volume 2 Issue 4, October 2013

Study on Extraction of Bamboo Fibres from Raw Bamboo Fibres Bundles Using Different Retting Techniques Varinder Kaur1, D P Chattopadhyay2, Satindar Kaur3 Department of Applied Chemical Sciences & Technology, Guru Nanak Dev University, Amritsar

1

Department of Textile Chemistry, Faculty of Technology & Engineering, The M. S. University of Baroda, Vadodara

2

Department of Food Sciences & technology, Guru Nanak Dev University, Amritsar

3

varinder_gndu@yahoo.com; dpchat6@gmail.com Abstract Pure bamboo fibres have been extracted by using three different retting techniques viz. Chemical assisted natural (CAN), Acid and Alkali retting. CAN and acid retted fibre bundles were further scoured using various concentrations of sodium carbonate. As the primary concern of this study is the end use of treated fibres for textile application, therefore, lignin content, tensile strength, weight loss, moisture content, whiteness and yellowness indices were measured. Lignin content analysis of the fibre bundles obtained showed that there was a remarkable reduction in lignin content after CAN retting. Scanning Electronic microscopy of the retted bamboo fibre bundles showed removal of short elementary fibres from their surfaces in appropriate amount, which further improved moisture content and overall physical properties of retted and scoured bamboo fibres.

Keywords Bamboo; Bamboo Fibre Bundles; Chemical Assisted Natural Retting, (CAN); Lignin

Introduction In textiles, market of bamboo clothing has suddenly raised due to the facts that it is ecofriendly, 100% biodegradable and can be completely decomposed in soil by micro organisms. There are two ways to process bamboo to make the plant into a fabric: mechanically or chemically. The mechanical way is by means of crushing the woody parts of the bamboo plant and then natural enzymes are utilized to break the bamboo walls into a mushy mass so that the natural fibers can be mechanically combed out, spun into yarn and then into fabric. Bamboo fabric made from this process is sometimes called bamboo linen.

Chemically manufactured bamboo fiber is regenerated cellulose fibre similar to rayon or modal. The bamboo fiber which is the current eco-fashion range is

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chemically manufactured by “cooking� the bamboo leaves and woody shoots in strong chemical solvents such as sodium hydroxide and carbon disulfide in a process known as hydrolysis alkalization combined with multi-phase bleaching.

The invention of bamboo fiber is the biggest contribution of mankind to protect naturally rare minerals/resources and ultimately the environment as a whole. The property that bamboo is highly renewable grass has resulted in its ecofriendly feature, which in turn leads to wide use in textile industry.

Repeated tests have proved that the bamboo fibre has a strong durability, stability as well as tenacity. The thinness and whiteness degree of fibre obtained from bamboo has been found to be similar to that of viscose staple fibre. Moreover, this fiber as natural cellulosic fiber can achieve natural degradation in soil and can be blended with other materials such as cotton, hemp, lyocell, modal fibre and so on.

The bamboo has been used in agriculture, handicraft, paper making, furniture and architecture for thousands of years; however, only recently efforts have been made to produce textile fibers from bamboo.

The worldwide research has been carried out on bamboo to study the structure, properties of bamboo fibre as well as extraction methods of bamboo fibre.

The quantitative analysis in chemical component of bamboo fibre resulted in that after degumming through a chemical treatment, the cellulose content in bamboo fibre reached more than 70%, which is the basic requirement of any fibre for its textile application.

The presence of lignin and hemicelluloses, on the other hand, somehow, reduces its applicability in textiles.

For better penetration of chemicals used in subsequent

Textiles and Light Industrial Science and Technology (TLIST) Volume 2 Issue 4, October 2013

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wet processing, fibre bundles separated from the culm of bamboo, need to undergo a process called retting, the most required stage for bast fibre extraction, especially in flax, bamboo, jute etc. which is a combined effect of temperature, moisture, bacteria or fungi, resulting in the fibrillation of the fibre bundle from gummy and cementing non-cellulosic substances like hemicellulose, lignin and pectin which enclose the cellulose.

treated with sodium carbonate 5-30 g/L, Lissapol-D 0.5 g/L and kept at 80oC for 45 minutes with fiber to liquor ratio 1:20. The concentrations of sodium carbonate were 5 g/L, 10 g/L, 15 g/L, 20 g/L and 30 g/L. At the end of scouring treatment, the fibers were neutralized with acetic acid and then thoroughly washed with distilled water.

In this work, a possible bamboo retting system is developed and properties of retted bamboo are also discussed.

Breaking strength and breaking extension of bamboo were tested using an Instron series IX fiber breaking strength machine at a constant temperature of 27oC and 65% relative humidity using ASTM Method D5035. Fiber weight loss was calculated using Eq. 1:

Material and Experiments Raw Bamboo (Figure 1 a) Raw bamboo harvested from Guru Nanak Dev University, Amritsar, India, was retted and extracted by following methods: 1) 1 B)

Chemical Assisted Natural Retting (CAN)(Fig.

First of all, nodes of raw bamboo (2-3 years old) were detached and residual part was cleaved in longitudinal direction to thin slabs with 15-20 cm in length and 1.5-2 mm in thickness by the slicer.

Finally, they were converted manually into fibre bundleswhich were then immersed in Zn(NO3)2 solution using material to liquor ratio 1:20 at 400C at neutral pH for 116 hours in BOD Incubatorand next boiled in water for one hour. The concentrations of Zn(NO3)2 were 1%, 2% and 3% (owf).

2)

Acid Retting (Figure 1 C)

The bamboo (2-3 years old) fibre bundles with the same dimensions as mentioned above were soaked in 1% HCl solution using material to liquor ratio 1:20 at room temperature for 45 minutes. Finally, they were washed with fresh water and dried under shadow.

3)

Alkaline Retting (Figure 1 D)

The bamboo (2-3 years old) fibre bundles with the same dimensions as mentioned above were soaked in 2gpl Na2CO3 and 0.5% Lissapol D solution using material to liquor ratio 1:20 at 80oC for 45 minutes.

Finally, they were washed with fresh water and dried under shadow.

Optimization of Na2CO3 Concentration for Scouring The CAN, acid and alkaline retted bamboo fibers were

Testing

(1) Where Wi is the initial weight of the raw bamboo fiber; and Wf is the final weight of treated bamboo fiber.

Moisture Content (T264-om-88) After retting, scouring and drying, the fibres were weighed in a tared weighing bottleand then dried for 2 hour in a preheated oven at 105oC. After that, the samples were cooled in desicator and then replaced the stopper, followed by opening the stopper for a moment to equalize the air pressure. The cooled samples were weighed again and placed back to the oven for I hour. The cooling and weighing of these samples were repeated as above for successive hourly periods until constant weight was achieved.

Moisture content (M %) of bamboo fibers was calculated from equation (2) following as: (2) Wi: Initial weight of the fibers Wf: Final weight of the fibers after drying The colorimetric properties like whitness and yellowness indices of the retted fibers (D65 illumination, 10o observer) were determined using a Spectraflash 600 colorimeter (Datacolor International).

Scanning Electron Microscopy Observations The deformation behavior of a single elementary retted bamboo fibre bundle was investigated by meas of scanning electron microscopy (SEM) using Quorum Q150RES (Supra 55- CARLZEISS) equipment.

Chemical Analysis The chemical composition of the original bamboo culm (without outmost layer) and retted bamboo fibre bundles was analyzed for lignin contents by using 175

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Textiles and Light Industrial Science and Technology (TLIST) Volume 2 Issue 4, October 2013

TAPPI standard T250-um-85.

Results and Discussion The 1% concentration of Zn(NO3)2 was selected in this study due to the better whiteness index with improved physical and mechanical properties of fibers with 1% compared to other treated with 2% and 3% (owf*) of Zn(NO3)2 (see Figure 2). Finally, they were washed with fresh water and dried under shadow.

TABLE 1 PHYSICAL AND MECHANICAL PROPERTIES OF BAMBOO FIBRE BUNDLE WITH RESPECT TO ZNNO3 CONCENTRATION

(*owf- on the weight of fibres) Tenacity (g/den)

Whiteness Index (Hunter lab)

Yellowness Index (Hunter lab)

Untreated

2.8568

17.63

47.51

ZnNO3 1%

1.8080

17.28

54.13

ZnNO3 2%

1.7287

14.37

53.87

ZnNO3 3%

1.7019

13.89

54.08

Concentration of ZnNO3 (owf)*

than that of the chemical assisted natural retted fibres.

But physical fibre separation was achieved through natural retting. On the other hand, the CAN retted fibres using 1% Zn(NO3)2, produced reasonable reduction in weight loss and tensile strength with acceptable whiteness & yellowness indices.

TABLE 2 COMPARISON OF PHYSICAL PROPERTIES OF NATURAL, ACID AND ALKALI RETTED FIBRES.

(W.I.- Whiteness Index; Y.I.- Yellowness Index) Type of retting

Weight loss (%)

Moisture content (%)

W.I.

Y.I

% Loss in Tenacity

Untreate d

0

6.63

17.63

47.51

-

CAN

5.0

11.01

17.28

54.13

36.72%

Acid

4.0

8.50

29.24

36.88

10.81%

Alkali

4.1

8.70

21.20

51.08

23.91%

FIGURE 2 a EFFECT OF CAN, ACID AND ALKALI RETTING ON WEIGHT LOSS (%) & LOSS IN TENACITY (%) OF FIBRES

FIGURE 2 PHYSICAL AND MECHANICAL PROPERTIES OF BAMBOO FIBRE BUNDLE WITH RESPECT TO ZNNO3 CONCENTRATION:

Figure 2a, 2b & 2c show the physical changes after different treatments. The removal of non-cellulosic matter by retting process enhanced the fibre separation from the bulk. The process also improved the capability of the fibres to absorb higher degree of moisture. Acid retting process highly enhanced the fibre appearance as seen from its whiteness index value. The drop in tenacity of the fibre was also comparatively low. Chemical assisted natural retting caused the highest loss in weight also at the cost of maximum loss in tenacity. The maximum loss in lignin was caused by chemical assisted natural retting process. Alkali retting gave an intermediate effect on fibre appearance and strength of fibre. Moisture content was determined as well. The results showed that the difference of moisture content of the acid treated and the alkali treated fibres was much lower 176

FIGURE 2 b EFFECT OF CAN, ACID AND ALKALI RETTING ON WHITENESS & YELLOWNESS INDICES OF FIBRES

FIGURE 2 c EFFECT OF CAN, ACID AND ALKALI RETTING ON LIGNIN CONTENT OF RETTED FIBRES

Textiles and Light Industrial Science and Technology (TLIST) Volume 2 Issue 4, October 2013

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1) Effect of Na2CO3 Concentration on Weight Loss of Natural, Acid and Alkali Retted Bamboo Fibres

(a)

(b)

Table 3.1 & Figure 3.1 show that the weight loss value increased up to 10 g/L, but slightly decreased in natural retting when the concentration of sodium carbonate was between 20 g/L and 30 g/L, and highly decrease in case of acid & alkaline retting. As minimum loss in lignin was found in case of alkali retting which is the clear indication of less removal of non-cellulosic material and resulting in less weight loss in comparision of CAN & acid retting.

TABLE 3.1 EFFECT ON WEIGHT LOSS OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

(c)

(d)

FIGURE 1. SEM IMAGES FOR SIDE-VIEW SURFACES OF BAMBOO FIBRE (a) RAW BAMBOO FIBRE,, (b) CAN RETTED BAMBOO FIBRE, (c) ACID RETTED BAMBOO FIBRE, (d) ALKALI RETTED BAMBOO FIBRE

Optimization of Na2CO3 Concentration During scouring Na2CO3 solution easily penetrated into fibres and so efficiently reducing noncellulosic substances as it can softly break off the connectivity in between noncellulosic and cellulosic components. In order to obtain the optimum sodium carbonate concentration for scouring, the pretreated (natural, acid & alkali retted) bamboo fibres were treated with different sodium carbonate concentration viz. 5 g/L, 10 g/L, 15 g/L, 20 g/L 30 g/L and the solution was made with Lissapol D 0.5% (OWF), fibre to liquor ratio 1:20 and treated at 80oC for 45 minutes followed by washing and finally dried in open. After the treatment, the weight loss, moisture content, physical and mechanical properties were tested to estimate the effect of sodium carbonate concentration.

Scanning Electron Microscopy Observations The surface properties of original & treated bamboo fibres were examined by SEM. A large quantity of gum & lignin in untreated bamboo can be observed.

As it can be seen in Figures 1a, 1b, 1c & 1d that the natural bamboo fibre consists of numerous elementary fibres. After natural retting, the number of elementary fibres is decreasing, meaning that the technical bamboo fibre is getting finer. Moreover, the inner structure of bamboo fibre becomes looser after treated with different retting techniques. As shown in all figures, clear cracks can be observed for, thus, produced natural bamboo fibre, indicating that the fibre can be easily separated into small bundles.

Concentration of Sodium carbonate(gpL) 5 10 15 20 30

Weight Loss (%) CAN retted Fibre 2.7 8.5 9.0 9.5 9.9

Acid retted Fibres 3 5.6 7.5 7.9 8.3

Alkali retted fibres 2.1 2.3 3.0 3.5 5.2

FIGURE 3.1 EFFECT ON WEIGHT LOSS (%) OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

2) Effect of Na2CO3 Concentration on Moisture Content of Natural, Acid and Alkali Retted Bamboo Fibres TABLE 3.2 EFFECT ON MOISTURE CONTENT (%) OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

Concentration of Sodium Carbonate (gpL) 5 10 15 20 30

Moisture content (%) CAN retted fibres 6.2 7.14 7.84 8.1 8.3

Acid retted fibres 4.2 5.7 7.0 7.8 8.1

Alkali retted fibres 5.7 6.3 7.14 7.89 7.93

Moisture content plays an important role in production of natural materials. The result presented in Table 3.2 & Figure 3.2 revealed that extracted fibres

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Textiles and Light Industrial Science and Technology (TLIST) Volume 2 Issue 4, October 2013

from the acid and alkaline retting technique showed overall lower moisture contents than natural retted fibres. It also showed that the moisture content value increased up to 15 g/L, but slightly decreased in natural & acid retting when the concentration of sodium carbonate was between 20 g/L and 30 g/L, and highly decrease in case of alkaline retting.

carbonate and the results are shown in Figure 3.4.

From both the table and figure, it is clear that all three processes of retting followed by treatment with different concentrations of sodium carbonate have a major drawback of yellowing in alkaline baths.

FIGURE 3.4 EFFECT ON YELLOWNESS INDEX OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES FIGURE 3.2 EFFECT ON MOISTURE CONTENT (%) OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

3) Effect of Na2CO3 Concentration on Whiteness Index of Natural, Acid and Alkali Retted Bamboo Fibres The retted bamboo fibres were treated using various concentrations of stock solution of sodium carbonate viz. 5 g/L, 10 g/L, 15 g/L, 20 g/L, 30 g/L and in the presence of Lissapol D 0.5% (owf), fibre to liquor ratio 1:20 and treated at 80oC for 45 minutes followed by washing and finally dried in open. After that the samples were tested for improvement in whiteness. It is found (Figure 3.3) that with increase in concentration of stock solution, the whiteness of the sample was decreased up to 20 g/L. Further increment showed a increasing effect on whiteness in case of natural and alkaline retting, but a steep fall has been observed in case of acid retting.

5) Effect of Na2CO3 Concentration on Tenacity of Natural, Acid and Alkali Retted Bamboo Fibres The average tenacity of natural bamboo fibres after different treatments were illustrated in Figure 3.5.

With the increase in the treatment intensity, the values of average tenacity initially decreased to 15 gpL, leading to a reduction in tenacity due to removal of non-cellulosic material. However, the concentration higher than 15 gpL was found to be less effective.

FIGURE 3.5: TENACITY (G/DEN) OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

Conclusions

FIGURE 3.3 EFFECT ON WHITENESS INDEX OF CAN, ACID & ALKALI RETTED BAMBOO FIBRES

4) Effect of Na2CO3 Concentration on Yellowness Index of Natural, Acid and Alkali Retted Bamboo Fibres The yellowness indices of treated samples were measured at different concentrations of sodium

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In this papr, three methods, CAN, acid and alkaline retting, were used to extract bamboo fibres bundles from raw bamboo fibre bundles along with the study on the effect of different concentrations of sodium carbonate on physical properties of fibres , among which CAN retting technique has been found to be the most effective pretreatment in wet processing of bamboo fibres.

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