Properties of Coconut Fiber

Properties of Coconut Fiber S Sengupta and G Basu, ICAR-National Institute of Research on Jute & Allied Fibre Technology, Kolkata, India r 2017 Elsevier Inc. All rights reserved.

1 2 2.1 2.2 3 3.1 3.2 3.3 3.4 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 6 References Further Reading

1

Introduction Fine Structure of Fiber Scanning Electron Microscopy Cross-Sectional View Physical and Mechanical Properties of Fiber Distribution of Different Properties of Coconut Fiber Diameter Distribution along the Fiber Length Inter-Relation between Two Fiber Properties Defects in Fibers Chemical Properties of Raw Coconut Fibers Chemical Composition Treatment with Water Treatment with Sulphuric Acid Treatment with Oxidizing Agent Chemical Properties of Retted Coconut Fibers Infrared Spectrum Analysis Crystalline Structure Analysis Thermal Analysis Differential Scanning Calorimetry Quality Specifications Retted Coir Fiber/White Fiber Brown Fiber Conclusions

1 1 2 2 4 5 6 8 11 12 12 13 14 14 14 15 15 15 17 17 17 18 18 19 20

Introduction

Coconut trees (Figure 1) are grown in the coastal regions in the wet tropical areas of India, Sri Lanka, Philippines, Indonesia, Malaysia, Fiji Islands, Vietnam, Hawaii Islands, Papua New Guinea, and Solomon Islands mainly. It is grown for the high oil content of the endosperm (copra), which is widely used in both food and non-food industries (e.g., margarine and soaps). The coconut trees are having a life span of about 80 years. Coconut is the seed of a species of palm, Cocos nucifera, and its fiber is the fibrous husk of the coconut shell (Figure 2). The most suitable soil for the coconut is rich alluvial or loam having adequate soil moisture either through well-distributed rainfall, percolation of soil moisture, and drainage system alongside the backwater. The coconut also yields well in lateral loamy or black clayey soil. It generally grows in an atmosphere of saline moisture, light wind with heavy and well-distributed rainfall and high-humidity and moderate climate (John, 1970). Large-production areas, in particular, are found along in these countries millions of people make a living from the coconut palm and its many products. Total world productivity has increased substantially from 35 MT around 1980 to almost 50 MT today (John, 1970; FAO, 2004, 2008). These palms flower on a monthly basis and the fruit take 1 year to ripen after 3–5 years of plantation. A palm tree may have fruit in every stage of maturity. A mature tree can produce 50–100 coconuts per year. Generally, a coconut weighs 1.0–1.2 kg per nut of which, weight of husk is around 300–400 gms (NRDC, 2009). This husk contains about 30% of textile quality fiber and rest small fibers (Pits) and small fragments (Pith). Green coconuts, harvested after about 6–12 months on the palm, contain pliable white fibers to dehydrated rigid brown fibers. These fibers are mainly used for making ropes/twines, carpets, furnishings, floor matting, wall decorative, fancy bags, etc. The quality of coconut fiber depends upon several factors, viz., agro-ecological conditions (rainfall, humidity, soil, etc.), variety of seedlings and most importantly on stage of harvesting and process employed for extracting the fiber. A good-quality fiber can be obtained from the green coconut husk when they are in naturally hydrated condition. The fiber at this stage found to be whiter, flexible, softer, and easy for chemical processing. However, as copra is the prime product of coconut, hence the dehusking is generally done when the coconut reached to its full maturity after 9 months and fibers are matured, dehydrated, and yellow to brown in color. Raw fibers (Figure 3) are retted conventionally in backwater for about 6–12 months (Manilal et al., 2010) to make it softer. Recently, chemical retting has been proposed by Basu et al. (2015) using a combination of Na2S, Na2CO3, and NaOH; which can improve fiber property after 2 h of treatment (Figure 4).

Reference Module in Materials Science and Materials Engineering

doi:10.1016/B978-0-12-803581-8.04122-9

1

2

Properties of Coconut Fiber

Figure 1 Coconut trees on the shore of backwater lagoon.

Figure 2 Cross section of matured coconut fruit.

2 2.1

Fine Structure of Fiber Scanning Electron Microscopy

The observation of the scanning electron micrographs of the raw fiber surface (Figure 5(a)) reveals cracks, voids, and parallel ridges, which are further connected with intermediate nodes perpendicular to fiber length forming more or less rectangular indentation. The non-uniformity seen in this fiber is probably caused by heterogeneous distribution of impurities, fat and waxy substances, and globular protrusions. The surface morphology of backwater retted fiber (Figure 5(b)) has more irregularities and impurities than the raw fiber, which might be due to formation of an additional salt coating through its backwater retting followed by air drying without washing. Comparing to raw and backwater retted coconut fibers, treated fibers appeared to be clean, with a smother surface and it is possible to observe a reduction on fats and waxes (Figure 5(c)). Alkali treatment removes the surface adhered impurities leading to formation of rough surface with pits which were not revealed on the surface of raw and backwater retted fibers.

2.2

Cross-Sectional View

The cross-section of fiber (Figure 6) is circular having central lumen. Presence of numerous voids around central lumen indicates its multi-fibrillar structure. The scanning electron micrograph shows the micro-fibrills by longitudinal parallel ridges. Uneven fiber surface with prominent cracks and micro-pores are detectable. Irregular wax-like deposition on the fiber surface masking the cracks,

Properties of Coconut Fiber

Figure 3 Raw fiber.

Figure 4 Retted fiber.

Figure 5 SEM view of coconut fibers (a) raw, (b) backwater retted, and (c) chemically retted (Basu et al., 2015).

3

4

Properties of Coconut Fiber

Figure 6 Cross section of a coconut fiber (Mishra and Basu, 2013).

and micro-pores in places, is visible in the micrograph. In this context, it may be noted that the fats and wax contents was found to be 1.03% as estimated by solvent extracted method.

3

Physical and Mechanical Properties of Fiber

Mechanical and physical properties of coconut fiber are shown in Table 1 where it is being compared with two allied popular lignocellulosic fibers viz., jute and sisal. Length and diameter Coconut fiber is notably thicker than sisal and jute. The diameter and length of coconut fiber, both are highly variable having range values 100–795 mm (average being 183 mm) and 44–305 mm (average being 320 mm), respectively. Linear density (59.2 tex) of coconut fiber is much higher as compared to jute (3.8 tex) and sisal (29.67 tex). However, apparent density and true density are 1.17 and 1.40 g cm
3 respectively comparable to jute and sisal. High linear density along with low length–diameter ratio (750) of coconut fiber indicates its suitability for coarse textile applications. Mechanical property Table 3 shows that, breaking tenacity (11.25 cN/tex) and initial modulus (200 cN/tex) of coconut fiber are notably lower than those of other two natural fibers. This may be due to its lower degree of crystallinity (45%) as compared to jute (58.7%) (Samanta et al., 2008) and sisal (71.7%) (Kalia et al., 2011). Coconut fiber showed relatively high extensibility of even up to over 21%, in contrast to the other natural fibers, jute (1.8%) and sisal (2.76%). High extensibility ultimately resulted in high-specific work of rupture (13.4 mJ/tex-m) of coconut fiber as compared to jute (2.8 mJ/tex-m) and sisal (4.41 mJ/tex-m). The extension of coconut fiber indicates spiraled cellulosic macro-molecular arrangement in the fiber having high angle of orientation (Stern and Stout, 1954). The fiber is having much higher degree of flexural rigidity (1473 mN-mm2) as compared to jute and sisal, may be attributed to its high-lignin content, coarseness, and nearly circular cross-section. Coconut fiber showed 59.3% instantaneous recovery and in total 81.5% recovery at 2 h on removal of compressive load. High-flexural modulus along with good resiliency indicates its high-shock resistance property. Frictional property Coefficient of friction for coconut fiber (0.35 in parallel direction and 0.30 in perpendicular direction) is lower with respect to jute (0.45 in parallel and 0.40 in perpendicular) and sisal (0.56 in parallel and 0.51 in perpendicular). This indicates its lack of inter fiber cohesiveness. This may be attributed, to the much less area of contact between the coconut fiber surfaces due to (1) more circularity in its cross-section as compared to jute and sisal, (2) hardness of fiber surface, (3) irregular fiber contour, and (4) high-flexural rigidity of coconut fibers, ultimately resulting in less welding effect. Electrical resistance It shows the maximum resistance of 4 Ω-kg m
2, while sisal and jute show 2.96 and 1.83 Ω-kg m
2, respectively. In semicrystalline polymers, current flows mainly through the crystalline regions (Pathania and Singh, 2009). Hence coconut fiber, which

Properties of Coconut Fiber

Table 1

5

Physical and mechanical properties (Bhattacharya et al., 2009)

Property parameter

Coconut

Jute

Sisal

320a (50.5) 183b 750 59.2 1.40 1.17 0.43

60 (32.1) 60c 1000 3.8 1.48 1.23 0.48

190 (36.9) 770 4052.6 29.67 1.45 1.2 0.45

Initial modulus (cN/tex) Specific work of rupture (mJ/tex-m) Flexural rigidity (mN-mm2) Coefficient of friction

11.25 (54) 21.5 (51) 200 13.4 1100 0.35

33.2 (45.7) 1.8 (41.3) 1900 2.8 22.1 0.45

28.2 (40.05) 2.76 (48.01) 1100 4.41 284.1 0.56

Moisture relationship Moisture regain at 65% RH (%) Longitudinal swelling (%) Transverse swelling (%) Water imbibition (%) Vertical wicking length after 24 h (mm)

11.7 0.6 15 58 2

13.5 0.07 25 92 7

10.92 0.08 15 64 17

Electrical properties Mass specific resistance (O-kg m
2)

4.0

1.83

2.96

Physical parameters Diameter (mm) Length (mm) Length–diameter ratio Linear density (tex) True density (g cm
3) Apparent density (g cm
3) Bulk density Mechanical behavior Breaking tenacity (cN/tex) Breaking extension (%)

a

Range 100–795 mm; Range 44–305 mm; c Modal value of filament. Figure in parenthenses indicates coefficient of variation of the corresponding parameter. b

is a low crystalline fiber, compared to jute and sisal, shows higher resistance. Additionally, presence of lignin up to 45%, which is hydrophobic in nature, inhibits the flow of current through the fiber matrix. High insulation property indicates its potentiality in use of electrical insulating materials. Microbial decomposition Accelerated testing for microbial decomposition reveals that coconut fiber retained 60% of its original strength even after 75 days, while, jute and sisal lost their strength within a period of 21 days. High durability of coconut fiber may be attributed to its higher lignin and much lesser hemicellulose and pectin content as compared to jute and sisal (Bhattacharyya and Paul, 1980; Rosa Medeiros et al., 2010). Moisture Coconut fiber showed good moisture regain (11.7%) and moderate to high water absorbency (63%). Moisture absorption resulted in moderate swelling of coconut fiber up to 50%. On the contrary, sisal despite having greater amount of cellulose (67–78%) in its macromolecule (Rahman and Khan, 2007), has low absorbency mainly due to its higher degree of crystallinity and wax content (Basu et al., 2011). It was observed that coconut fiber shows an apparent hydrophobic nature with water. This may be attributed to high carbon to carbon (C‒C) and carbon-to-hydrogen (C‒H) bonds of surface lignin (Mahato et al., 2009), which initially hinder the aqueous treatment.

3.1

Distribution of Different Properties of Coconut Fiber

Wei and Gu (2009) analyzed length and fineness characters of coconut fibers (Table 2) from a bunch of randomly taken from a fiber stack. The fiber-length distribution is given below. It is found that longer fibers usually have higher diameters. Table 3 summarizes the statistical distribution data, viz., extreme values, mean, median, mode, coefficient of variation (CV), skewness, standard error of skewness, kurtosis and standard error of kurtosis, of property parameters of coconut fiber. It is clear from the table that all the physical properties have high variation. Majority of the fibers are lying in the range of 4–12 cm length,

6

Properties of Coconut Fiber

Table 2

Length and fineness distribution

Parameters

No of fibers Weight of fibers

Fiber-length distribution Range of fiber length, mm

% of Fiber

15–145 35–225

81.95 88.34

100–200 mm diameter, and 10–20 tex linear density. This is mainly attributed to their natural inheritance. In coconut fiber, this variability is much higher due to poor extraction process and unorganized collection which mixes fibers of different maturity and varieties. To test the normality of all the characteristics, its skewness and kurtosis were evaluated. All the properties were shown to have skewed asymmetric curve. Similarly, kurtosis values, which are not zero, indicate that none of the characteristics follow normal distribution; either it is leptokurtic (positive value) or platykurtic (negative value). The distribution curves are shown in Figure 1. Since, it is evident that all the characteristics are asymmetric in nature; Kolmogorov–Smirnov (K–S) goodness-of-fit test (Massey, 1951; Miller, 1956) is applied at a significance level aZ0.5 to ascertain the best-fit curve, where highest K–S probability value represents the best asymmetric curve. Table 4 shows the K–S distribution and K–S probability values of fiber length for different probability density functions. The highest K–S probability value of 0.199 for Weibull function indicates the best-fit function for that property. All other properties of coconut fiber were tested likewise and the best-fit functions of different properties along with its K–S probability value are listed in Table 5. An extensive work (Sengupta, et al., 2014) deals with variation in different physical properties within a lot of coconut fibers randomly selected from mixture of fibers taken from a specified agro-ecological region in India. Natural fibers inherently differ from each other to a great extent. Information on average values of various property parameters and variability of each property parameters is essential to a processor to identify or to design processing machines to convert the fiber to value-added products. For any industrially processable fiber crop, an evenly distributed property parameter is most desirable to the processor. The results (Table 3) show that all the major property parameters of coconut fiber are highly variable and follows asymmetric distribution curve. It indicates the chance of coming out with highly variable textile products from processing machines in spite of taking all the possible measures to produce regular thread-like materials (twines and cordages) and any finer sheet-like materials. High variability in fiber length (Figure 7(a)) causes high hairiness protruded from thread surface. It becomes difficult to engineer finer materials if the diameter is highly variable. High variability in diameter and linear density indicates that coconut fiber may be used in making much coarser materials like house-hold ropes and cordages. However, length-wise segregation of fiber would solve the problem to a considerable extent. Considering the asymmetric distribution (Figure 7(a)), the fibers may be segregated in following three major length-groups, namely (1) long, (2) medium, and (3) short. Figures reveal that number of medium length fiber is substantially higher than short followed by long fibers. The distribution of diameter as well as linear density values also shows nearly similar trend. In this case number of coarse fiber is substantially higher than medium followed by fine fibers. So, the fiber mix may also be sorted by diameter or linear density (Figures 7(b) and 7(c)). Due to differences in linear densities, segregation may be done by centrifugation or winnowing the fiber mix. The segregated fibers may be used for producing three different groups of materials. Long and coarse fibers may be used for producing conventional ropes and coarse mats, while medium length and fine fiber may be used for making finer textiles materials with improved property parameters, either elementarily or in blends with other fibers. Short fibers may be used in making flexible or semi-rigid composites and also used as geofibre (Balan, 2004) for soil stabilization. It may be worth noting that distribution of mechanical property parameters (viz., breaking tenacity and elongation) are much less asymmetric (Figures 7(d) and 7(e)) as compared to the dimensional property parameters. The coefficient of variation of breaking tenacity (47.3%) and breaking extension (37.5%) is lower than the CV of length (50.9%) and diameter (52.9%). Distribution of specific work of rupture and flexural rigidity has been shown in Figures 7(f) and 7(g), respectively. Specific flexural rigidity values were highly asymmetric with CV, 94.3% (Figure 7(h)). The increased coefficient variation, in this case, may be attributed to the combination of the two highly variable physical parameters, flexural rigidity and linear density. The problem has been further aggravated due to variation in diameter along the length of individual fiber.

3.2

Diameter Distribution along the Fiber Length

Figure 8 shows variation in fiber diameter along the fiber length. Sixty fibers were selected randomly and divided into three equal parts as fine, medium, and coarse according to its linear density. Diameter of all the fibers was measured from base to tip in 1 cm interval. The diameter of different fibers gradually increases from base to a mid-point, and then starts decreasing till the tip ends. The diameter of coarse fiber changes from 493 to 263 mm having the highest diameter at 550 mm with the coefficient of variation of 21.2%. The diameter of fine fiber changes from 93 to 91 mm having the highest diameter of 187 mm with the coefficient of variation of 25.6%. This may be one of the major reasons for high coefficient of variation of different fiber properties. Figure 2 reveals that individual fiber possesses variable diameter along its length tapering off at both the ends.

Table 3

Property parameters of various physical characteristics of coconut fiber (Sengupta et al., 2014)

Characteristics

Sample size

Length (cm) Diameter (mm) Linear density (tex) Breaking tenacity (cN/tex) Breaking extension (%) Specific work of rupture (mJ/tex-m) Flexural rigidity (mN-mm2) Specific flexural rigidity (mN-mm2)  104

102 102 102 62 62 62 33 34

Minimum

Maximum

3.8 83.3 4.6 3.85 7.7 7.1

26.4 550 140 47.1 51.6 172.4

36.8 500.3

2084.3 15343.6

Mean

14.08 244.6 36.8 14.1 28.2 57.6 811.4 3524

Median

Mode

Coefficient of variation

Skewness

Standard error of skewness for normal distribution

Kurtosis

Standard error of kurtosis for normal distribution

12.9 200 25.2 11.8 28.3 51.3

5.8 166.6 Multiple 10.3 Multiple Multiple

50.9 52.9 80.4 47.3 37.5 56.6

0.221 0.818 0.993 1.65 0.19 0.92

0.239 0.233 0.23 0.3 0.31 0.31


1.328
0.445 0.05 3.12
0.66 0.99

0.473 0.463 0.469 0.61 0.6 0.6

864.1 2554.5

1121.4 Multiple

69.7 94.3

0.68 2.58

0.42 0.4


0.08 7.1

0.82 0.78

Properties of Coconut Fiber 7

8

Properties of Coconut Fiber Table 4 Estimation of goodness of fit of different distribution curves for some physical property parameters of coconut fiber (Sengupta et al., 2014) Property parameter

Probability density function (PDF)

K–S da

K–S pb

Length

Weibull Extreme Rayleigh Lognormal Exponential Gamma

0.1012 0.108101 0.116818 0.119202 0.2 0.102

0.1993 0.145378 0.094139 0.083099 o0.05 o0.05

a

K–S d ¼ Kolmogorov–Smirnov distribution K–S p ¼ Kolmogorov–Smirnov probability

b

Table 5

Relations of different physical characteristics (Sengupta et al., 2014)

Variable X

Variable Y

Length Length Length

Diameter Linear density Breaking tenacity

Length Length Length Length

Breaking Load Breaking extension Specific work of rupture Flexural rigidity

0.834
0.272
0.743 0.423

Length Diameter Diameter

Specific flexural rigidity Linear density Load


0.07 0.893 0.785

Diameter Diameter Diameter Diameter Diameter Linear density Linear Density

Breaking tenacity Breaking extension Specific work of rupture Flexural rigidity Specific flexural rigidity Breaking tenacity Breaking Load


0.122
0.437
0.826 0.764
0.33
0.207 0.804

Linear Linear Linear Linear

Breaking extension Specific work of rupture Flexural rigidity Specific flexural rigidity


0.316
0.934 0.739
0.302

density density density density

Correlation coefficient 0.759 0.799 0.293

Best-fit equation

Degree of freedom

Calculated t-value

p-Value

y¼0.533x2
5.525x þ 153.1 y¼0.180x2
2.679x þ 23.12 y¼
0.030x2 þ 1.037x þ 5.720 y¼1.809x2
19.31x þ 208.8 y¼
0.451x þ 33.26 y¼115.2e
0.07x y¼
31.21x2 þ 1146. x
9295 y¼
84.74x þ 4948 y¼0.255x
21.31 y¼
0.001x2 þ 3.360x
226.0 y¼13.83e
8E
0x y¼12.45e0.005x y¼190.3e
0.00x y¼117.3e
0.07x y¼
87.82x þ 4951 y¼
0.045x þ 14.07 y¼
0.066x2 þ 15.83x þ 0.656 y¼29.00e
0.00x y¼90.86e
0.02x y¼87.72e0.034x y¼
36.43x þ 5457

60 60 60

8.4 7.48 0.592

0.00001 0.0001 0.555

60 60 60 30

10.2
2.44
6.56 0.634

0.00001 0.017 0.0002 0.53

30 60 60


0.4 15.38 11.5

0.69 0.00001 0.0001

60 60 60 30 30 60 60


1.24
2.94
7.07 6.27
1.99
1.91 8.7

0.219 0.0045 0.00001 0.00003 0.054 0.06 0.0001

60 60 30 30


3.42
7.78 7.98
1.79

0.0011 0.00001 0.00002 0.082

denotes the insignificance of value.

3.3

Inter-Relation between Two Fiber Properties

Among the fiber properties studied, length, diameter, and linear density can be studied easily. A rough estimation of these parameters can be done without any sophisticated instrument. A simple stainless steel scale graduated in 10 divisions of a centimeter and an ordinary magnifying glass may be used to measure length and diameter, whereas a simple weighing balance may be used to get linear density. Therefore, it has been tried to understand the relationship (Table 5 and Figures 9(a)–9(c)) between these three parameters individually with other fiber properties (Sengupta et al., 2014) so that those properties can be predicted from these three primary parameters. The properties which are poorly correlated and insignificant with fiber length are not shown graphically. Length is the most important primary parameter to judge fiber quality. This study shows a good correlation of fiber length with diameter (0.759), linear density (0.799), braking load (0.834), and specific work of rupture (0.743), out of which first three are positively correlated, whereas specific work of rupture is negatively correlated, i.e., with increase of length, it decreases. The significance of these relations has also shown by student t-test (significance level aZ0.5) and corresponding p-value. Tenacity, breaking extension, flexural rigidity, and specific flexural rigidity are poorly correlated with length and this is supported by the

Properties of Coconut Fiber

Figure 7 (a) Length distribution of coconut fiber. (b) Diameter distribution of coconut fiber. (c) Linear density (fineness) distribution of coconut fiber. (d) Strength distribution of coconut fiber. (e) Breaking extension distribution of coconut fiber. (f) Specific work of rupture distribution of coconut fiber. (g) Flexural rigidity distribution of coconut fiber. (h) Specific flexural rigidity distribution of coconut fiber.

9

10

Properties of Coconut Fiber

Figure 8 Diameter distribution along the fiber length; (a) coarse fiber (62 tex), (b) medium fiber (25 tex), and (c) fine fiber (9.5 tex) (Sengupta et al., 2014).

t-test and p-values. Table 5 shows the best-fit equations for each relation. Diameter, linear density, and braking load follow the second order polynomial, whereas specific work of rupture follows exponential curve. Figures 9(a)–9(d) show the effect of fiber length on diameter, linear density, braking load, and specific work of rupture of fibers. Diameter is another important primary parameter for fiber quality assessment. This study shows a good correlation of fiber diameter with length (0.799), linear density (0.893), braking load (0.785), specific work of rupture (0.826), and flexural rigidity (0.764) out of which first three are positively correlated. The significance of these relations is also shown by student t-test (significance level aZ0.5) and corresponding p-value. Tenacity, breaking extension, and specific flexural rigidity are poorly correlated with diameter and this is supported by the t-test and p-values. Table 5 shows the best-fit equations for each relation. Diameter is related with linear density by linear equation and load by second order polynomial, whereas other properties exponentially. Figures 9(a) and 9(e)–9(h) show the effect of diameter on length, linear density, breaking load, specific work of rupture, and flexural rigidity of fibers. Linear density is an important primary fiber quality for processability point of view. This study shows a good correlation of linear density with length (0.799), breaking load (0.804), specific work of rupture (0.934), and flexural rigidity (0.739), out of which length, braking load, and flexural rigidity are positively correlated, i.e., with increase of linear density other parameters increases, whereas specific work of rupture is negatively correlated, i.e., with increase of linear density it decreases. The significance of these relations is also shown by student t-test (significance level aZ0.5) and corresponding p-value. Tenacity, breaking extension, and specific flexural rigidity are poorly correlated with linear density and this is supported by the t-test and p-values. Table 5 shows the best-fit equations for each relation. Diameter and braking load follow the second order polynomial, whereas others are related exponentially. Figures 9(b) and 9(i)–9(k) show the effect of linear density on length, braking load, specific work of rupture, and flexural rigidity of fibers. In all the cases, it is apparent that the relations of easily measurable parameters (length, diameter, and linear density) with breaking tenacity and specific flexural rigidity are very poor due to the combined effect of very high variability of linear density as well as basic parameter, i.e., breaking load or flexural rigidity. High linear density variation may be due to the age of the fibrous elements within or between the nuts. On reaching the maturity level, deposition of biological elements increases in both longitudinal and radial directions of the individual fibrous element as duration increases before harvesting. Furthermore, the diameter as well as linear density also varies along the length of fiber. The breaking extension is always poorly correlated, as it is mainly governed by weak places and structural defects of fibers and not by the basic fiber parameters. That is why the extensibility of fibers is unpredictable by length, diameter, and linear density. The best-fit equations with significant correction coefficient help to predict major fiber quality parameters (linear density, breaking load, specific work of rupture, and flexural rigidity) by easily measurable parameters (length and diameter). Since, the grading is generally done at growers’ field or at the market yard, our aim is to assess the quality characteristics of fiber in shorter period of time adopting minimum number of easily measurable parameters. The predicted values will help to grade the coconut fiber lot in farmers’ field by measuring length and diameter using ordinary scale and magnifying glass. By this process the farmer will fetch good economic return from the fiber. Textile and non-textile products prepared from the fibrous materials depend on fiber property and structural parameters of end product (Goswami et al., 1977). The major dimensional and mechanical property parameters of fibers include length, diameter, linear density, strength, elongation, work of rupture, and flexural rigidity. Longer and finer (lower linear density) fiber produces stronger, regular, and less hairy products. Soft fiber (low flexural rigidity) requires much less energy to twist a fiber bundle to make

Properties of Coconut Fiber

11

300 200 100

120 100 80 60 40 20

0

(a)

15

20

25

30

0

Linear Density (tex)

Specific work of rupture (mJ/tex-m)

100 80 60 40 20 0 10

(d)

15

20

25

30

Flexural rigidity (mN-mm2)

400 350 300 250 200 150 100 50 200

(g)

300

400

500

20

25

400 200 0

30

5

10

(c)

100.0 200.0 300.0 400.0 500.0 600.0

15

20

25

30

500

600

Length (cm)

1200 1000 800 600 400 200 0 0

(f)

100

200

300

400

Diameter (micron)

3500

1400

3000 2500 2000 1500 1000 500

1200 1000 800 600 400 200 0

0 0

100

600

Diameter, micron

15

Diameter (micron)

0 100

600

1400

160 140 120 100 80 60 40 20 0 0.0

(e)

Length (cm)

0

10

Length (cm)

120

5

5

(b)

140

800

0

0

Length (cm)

0

1000

Breaking load (cN)

10

1200

Breaking load (cN)

5

0

Breaking load (cN)

400

Spefific Work of Rupture, mJ/tex-m

1400

140

500 Linear density (tex)

Diameter (micron)

600

200

300

400

500

Diameter (micron)

(h)

0

600

(i)

20

40

60

80 100 120 140 160

Linear Density (tex)

Flexural rigidity (mN-mm2)

Specific work of rupture (mJ/tex-m)

140 120 100 80 60 40 20

5000 4000 3000 2000 1000 0 0

0 0

(j)

6000

20

40

60

80

100 120 140 160

Linear density (tex)

(k)

20

40

60

80

100

120

140

Linear density (tex)

Figure 9 (a) Effect of fiber length on diameter. (b) Effect of fiber length on linear density. (c) Effect of fiber length on breaking load. (d) Effect of fiber length on specific work of rupture. (e) Effect of diameter on linear density of fiber. (f) Effect of diameter on breaking load of fiber. (g) Effect of diameter on specific work of rupture of fiber. (h) Effect of diameter on flexural rigidity of fiber. (i) Effect of linear density on breaking load of fibers. (j) Effect of fiber linear density on specific work of rupture. (k) Effect of fiber linear density on flexural rigidity.

thread-like material. Soft fiber also yields stronger and softer textile materials. The increase in linear density, caused due to increased deposition of lignocellulosic matters, restricts intermolecular movements during bending, resulting in high rigidity. Toughness (specific work of rupture) depicts the combined effect of fiber strength and elongation, and it indicates end use performance of the product. The stated fiber parameters also decide some other important product functional parameters, i.e., handle, insulation, etc.

3.4

Defects in Fibers

Four main defects are identified namely (1) coconut peat, a dust-like matter of small particle size (10.64%); (2) mid-joint, a sticky bark-like matter at the middle of fiber (6.03%), (3) branched fiber, branching out from the main fibrous element (2.35%), and (4) insect bite (2.31%). On physical verification, it is found that the coco-peat would be removed from the fibers during their mechanical processing, such as opening, cleaning, and drawing. Similarly, the mid-joints would also be opened up during the same processing machines. So, coco-peat and mid-joints may be considered as minor defects. Though, weight loss to an extent of 10% (or more) may cause monitory loss to the fiber processing units. Some branched fiber and insect bitten may be remained in the fibers even after initial mechanical processing and this would not be suitable for mechanical conversion to finer or

12

Properties of Coconut Fiber

Figure 10 (a) Branched fiber. (b) Insect bite. (c) Coconut pit. (d) Mid-joint.

value-added end products. So, branched fiber and insect bite may be considered as the major defect. Different defects are shown in Figures 10(a)–10(d) (Sengupta et al., 2014). Defects in fiber are one of the major parameters of fiber quality in terms of its processability, generation of waste and quality of the output of the machine. Minor defects are generally eliminated during processing of fiber and most of them are generally dropped down during processing in the machines and do not affect the end product quality. However, minor defects have some economic importance due to the waste generated from fiber lot. Among the major defects, branched fiber may cause generation of hairiness on the yarn surface. Insect bitten fiber may affect strength and appearance properties of the intermediate or of the end product.

4 4.1

Chemical Properties of Raw Coconut Fibers Chemical Composition

The chemical composition of coconut is given in Table 6, which shows that brown coconut fiber contain relatively low amounts of cellulose but have high-lignin content. The exceptionally high-lignin content implies that the available dyeing and bleaching techniques for textile fibers cannot simply transferred to coconut fibers/products.

Properties of Coconut Fiber

13

Table 6 Chemical composition of raw coconut fiber (% of bone dry weight)

Table 7 Expt. no.

1 2 3 4 5 6 7 8

9

10

11 12 13 14

Constituent

%

a-Cellulose Lignin Hemicelluloses Pectin Ash Fats and waxes

38.4 31.8 24.5 0.5 1.6 1.1

Effect of treatments on physical and mechanical properties of coconut fiber (Basu et al., 2015) Treatment

Control Backwater retted Water at boil for 2h Steaming at 121 1C for 2 h 20% NaOH at boil for 2 h 40% Na2S at boil for 2 h 15% Na2CO3 at boil for 2 h 40% Na2S, 20% NaOH at boil for 2 h 40% Na2S, 15% Na2CO3 at boil for 2 h 40% Na25, 15% Na2CO3, 20% NaOH at boil for 2h 3% H2O2 for 2 h at 80 1C(pH-11) 2% NaIO4 at boil for 2 h HCl (35%) at 30 1C for 1 h H2SO4 at 30 1C for 1h

Physical property

Mechanical property

Weight loss(%)a

Diameter (mn)

Linear density (tex)b

L/D ratio

Flexural rigidity (cN mm2)

Breaking tenacity (cN/tex)

Breaking elongation (%)

Specific work of rupture (mJ/tex-m)

– – 2.60 (10)

345 (57) 282 (37) 381 (55)

53 (58) 44 (49) 52 (46)

695 (61) 748 (58) 689 (48)

1273 (49) 613 (57) 1235 (64)

11.3 (67) 14.0 (53) 12.1 (46)

21.5 (33) 27.1 (39) 18.8 (27)

12.1 (42) 12.0 (58) 13.9 (43)

7.20 (7)

347 (56)

48 (58)

712 (62)

1177 (67)

12.2 (56)

19.2 (41)

14.5 (42)

12.2 (13)

341 (53)

45 (67)

789 (73)

1034 (49)

13.8 (39)

24.7 (36)

19.3 (48)

17.6 (8)

227 (57)

41 (47)

917 (54)

731 (76)

13.4 (41)

27.8 (29)

18.1 (41)

11.5 (9)

359 (54)

49 (57)

742 (63)

1084 (49)

11.9 (46)

22.4 (42)

12.5 (56)

21.7 (9)

249 (52)

43 (59)

898 (72)

893 (56)

11.8 (87)

21.5 (37)

18.2 (56)

20.1 (11)

255 (57)

48 (47)

915 (59)

921 (64)

12.1 (65)

21.2 (35)

17.4 (47)

28.4 (13)

225 (41)

34 (52)

991 (63)

361 (55)

14.2 (59)

21.3 (33)

21.6 (43)

13.6 (9)

251 (59)

39 (39)

891 (48)

890 (53)

11.7 (57)

19.9 (36)

17.5 (39)

6.40 (7)

276 (63)

52 (46)

734 (49)

1062 (48)

8.4 (51)

14.3 (45)

9.5 (47)

250 (64)

35 (57)

1073 745 (67) 2.9 (167) 3.90 (98) 0.5 (99) (64) Immediate surface charcoaling at and above 30% concentration and fiber became brittle during storage even after alkaline neutralization

37.4 (23)

a

Results shows the mean value of ten repeat tests. Tex is the weight of l000 m long fiber in gram. The figures in the parenthesis indicates CV% of the corresponding value.

b

4.2

Treatment with Water

Treatment with water (Table 7) at boil and steaming for 2 h causes weight loss of 2.6 and 7.2% respectively in raw coconut fiber. Water treatment at boil leaches out part of the water soluble matters. However, under steaming, water insoluble matter including pectin, low-molecular-weight hemicellulose fraction apparently gets leached out contributing to additional weight loss. The flexural rigidity value of 1273 cN mm2 of the raw coconut fiber has lowered to 1235 and 1177 cN mm2 on boiling and steaming the fiber for 2 h respectively (Basu et al., 2015).

14

Properties of Coconut Fiber

4.3

Treatment with Sulphuric Acid

The treatment (Table 7) using H2SO4 (40% and above) at ambient temperature, results in surface carbonization with gradual solubilization (complete or partial) of the fiber. However, for concentration of 30% and below for H2SO4, the fibers resist the treatment for 1 h without any surface carbonization. The action of HCI is milder than H2SO4, which shows no surface carbonization under the treatment conditions. However, both the treatments made the fiber brittle during storage even after alkali neutralization, probably due to hydrolysis of cellulose polymers by the acids (breakage of the b-1,4-glycosidic bonds of cellulose) (Huang and Fu, 2013).

4.4

Treatment with Oxidizing Agent

The treatment (Table 7) of strong oxidizing agent NaIO4 with coconut fiber (alkaline pH) results in more reduction in tensile properties than in flexural rigidity. This may be due to possible chain scission of l,2-diols linkages of cellulose to form aldehydes and ketones (Hong et al., 2009). Oxidizing agent, H2O2 (alkaline pH) is also not found to be sufficiently suitable to reduce the fiber flexural rigidity, though there is no adverse effect observed on the tensile properties of the fiber. The treatment with Na2S (Treatment No. 6), showed high weight loss (17.6%) and larger reduction in flexural rigidity. diameter, linear density and thereby increased the length to diameter ratio, improving the mechanical properties of coconut fiber. The reaction of Na2S can be explained on the basis of its hydrolysis to convert into NaHS and finally to NaOH. The high alkalinity at elevated temperature of the treatment partially hydrolyzes the components of coconut fiber. Apart from this, NaHS reacts with lignin to introduce -SNa group which increases its acidity and solubility in alkaline medium. The Na2S being a reducing agent retards the rate of hydrolysis and oxidation of cellulose (Tomlinson, 1950) causing lower damage to the fiber structure. Treatment of coconut fiber was also carried out using alkaline aqueous solution of NaOH and Na2CO3 separately. The individual treatment of NaOH and Na2CO3 has moderate reducing effect on fiber flexural rigidity. The combination of Na2S with NaOH reduces the flexural rigidity and breaking tenacity more than that of combination of Na2S with Na2CO3. However, the binary treatments (Treatment No. 8 and 9), show lesser effect on fiber softening properties than the individual treatment of Na2S (Treatment No. 6). The ternary combination of Na2S, Na2CO3, and NaOH treatment (Treatment No.10 of Table 7) is found to be most effective in all respect. The combination of 40% Na2S, 15% Na2CO3, and 20% NaOH causes highest weight loss (about 28%) without affecting the tensile property. The treatment also reduced flexural rigidity, linear density, and diameter significantly resulting in enhancement of length to diameter ratio (Table 1). It is assumed that the combination of alkalis (NaOH, Na2CO3) might enhance the effect of Na2S. Alkalis swell the structure of the fiber causing easy penetration of Na2S for disruption of internal fiber structure. Further, in any natural fibers, the addition of alkali reduces the surface negative ion concentration by the excessive supply of Na þ ion, which facilitates better reaction of the chemical with the fiber. Alkalis also tend to reduce the surface tension of the natural fibers and helps in saponification and emulsification of fat and wax (present on fiber surface of most natural fibers), which otherwise hinders the water based treatments. Besides pure cellulosic components, hemicelluloses and alkali soluble lignin part are solubilised or precipitated out by alkalis. The presence of Na2CO3 provides some action of detergency to the treatment solution and thus helps in holding the dirt and other insoluble impurities in the suspension from depositing on the fiber surface.

4.5

Chemical Properties of Retted Coconut Fibers

The change in major constituents of raw coconut fibers, due to backwater and newly developed chemical retting is given in Table 8. The chemically retted fiber shows considerably higher a-cellulose (54.2%) than both backwater retted (39.6%) and raw (38.4%) coconut fiber. The increase in cellulosic content is also evident in FTIR and XRD of chemically retted fibers. Chemical treatment resulted in reduction of lignin content of raw coconut fiber from 31.8 to 26.3%. The reduction of lignin content possibly decreases the flexural rigidity of the fiber up to a certain extent. The analysis also reveals notable reduction in other constituents of the fiber like hemicelluloses, pectin, fats, and waxes, and ash content due to chemical treatment. The removal of constituents other than cellulose (viz., lignin, hemicelluloses, pectin, fats, and waxes), which are not contributing toward the tensile parameters probably cause much better mechanical properties in terms of higher breaking tenacity, and work of rupture in chemically retted fiber. The Table 8

Chemical composition of coconut fiber (weight % on oven dry basis)

Components

Raw/unretted

Backwater retted

Chemically retted

a-Cellulose Lignin Hemicelluloses Pectin Ash Fats and waxes

38.4470.7 31.8470.48 24.5470.15 0.570.01 1.4170.03 1.1270.001

39.6470.21 31.9570.02 22.7370.9 0.3770.03 1.4670.06 1.0970.07

54.1670.13 26.2970.05 14.0470.01 0.00 0.7670.03 0.7570.01

Source: (Basu et al., 2015).

Properties of Coconut Fiber

15

Figure 11 FTIR Spectra of coconut fiber (a) raw, (b) backwater retted, and (c) chemically retted (Basu et al., 2015).

trend of removal of constituents like, hemicelluloses, pectin, and fat and wax matters is also evident in backwater retting, but the extent of removal is trivial.

4.6

Infrared Spectrum Analysis

Figure 11 shows the FTIR spectra of the (a) raw (b) conventionally backwater retted, and (c) accelerated chemically retted coconut fiber. It can be seen from the three spectra that, no considerable change occurs either in position or in appearance/disappearance of the peaks. However. there was a change in intensity of some of the peaks, such as 1250, 1332, and 1513 cm
1 observed. The broad and intense peak at B3340 cm
1 suggesting OH stretching vibrations from cellulose and lignin intensified in chemical retted fibers. The characteristic bands of hemicelluloses and lignin observed around 1741 cm
1 due to the conjugated 4C¼ O stretching of ester and aldehyde reduced more in chemically treated coconut fiber than the conventionally backwater retted fiber. No change is observed in b-glucosidic linkage peak of celluloses at 897 cm
1 in backwater retted and raw fiber. However the same peak intensifies slightly in case of chemically retted fiber. The C‒O‒C stretching absorption peak of cellulose at 1038 cm
1 remain similar in the three fibers (Samal et al., 1995; Samanta et al., 2008). This proves backwater retting and chemical retting do not affect the celluloses part of coconut fibers. However. the absorption peaks at 1250 cm
1 correspond to CO‒ stretching of esters. ethers and phenols groups attributed to the presence of waxes in the epidermal tissue (Brigida et al., 2010) and at 1513 cm
1 correspond to lignin aromatic ring stretching (Mahato et al., 2009), both drastically reduced in the chemically retted fiber due to the removal of wax and lignin respectively during chemical retting/softening of fiber.

4.7

Crystalline Structure Analysis

Figure 12 shows the radial X-ray diffractogram of the three coconut fiber samples. Crystallinity Index (C.I.) of the chemically treated coconut fiber (54%) is much higher than the C.I. of the raw fiber (37%) and retted fiber (42%) as estimated by amorphous subtraction method. The diffractogram peaks (mainly peak 002) for the chemically retted fiber intensified considerably and got sharpened than the others indicating an enhancement of crystalline perfection due to removal of non-crystalline material like lignin, hemicellulose, pectin, etc., by the chemical treatment. Similar results were also reported by different authors (Varma et al., 1984; Sreenivasan et al., 1995) while discussing the effects of alkali treatments on coconut fibers.

4.8

Thermal Analysis

The results of thermogravimetric analyses for raw, backwater retted and chemically retted coconut fibers are shown in Figure 13 and summarized in Table 9. It can be seen that, decomposition of fibers are characterized by the temperature range. The initial decomposition of fiber takes place for evaporation of water and volatile substances (low-molecular-weight waxes and fats) occurs between room temperature and 150 1C. The second weight loss corresponds to hemicelluloses degradation. starts at about 190 1C.

16

Properties of Coconut Fiber

Figure 12 XRD curves of coconut fiber (Basu et al., 2015).

Figure 13 TG curves of coconut fiber (Basu et al., 2015).

Weight loss occurs between 290 and 360 1C mainly corresponds to cellulose degradation. Lignin degradation starts at about 280 1C and continues even above 500 oC (Rosa et al., 2009). The chemical treatment have a considerable change on the thermal degradation behavior of coconut fibers as compared to raw and backwater retted fibers. which possess resembling profile of weight loss. The initial weight loss attributed to evaporation of water and volatile substances was found to be lowest (6.8%) for chemically retted fibers due to removal of some easily hydrolyzed substances (waxes and fats) during chemical treatment. The comparatively higher weight loss (8.5%) for evaporation of water observed in backwater retted fibers than raw (7.4%) fiber possibly due to the extra moisture adsorbed by the salty layer present on fiber surface (as constituent analysis reports similar content of fats and waxes). Chemically treated fiber showed markedly lower weight loss of 21.8 and 21.5% under the transition temperature range of 150–330 and 590–700 1C respectively. as compared to raw and backwater retted fiber. The comparatively lower weight Joss occurred in chemically treated fiber for the temperature range, is indicating the reduction in hemicelluloses and overall lignin content than the other two fibers. Chemically retted fiber showed

Properties of Coconut Fiber

Table 9

17

Thermogravimetric results of coconut fibers Residuea left (%)

Coconut fiber

Transition temperature range (1C)

Raw

30–150

7.39

2.8

Backwater retted

150–330 330–590 590–690 30–150

27.13 39.24 23.43 8.46

2.6

150–330 330–590 590–690 30–150 150–330 330–590 590–690

26.77 39.12 23.02 6.84 21.82 49.07 21.54

Chemically retted

Weight loss (%)

0.7

a

Degradation residue at 700 1C Source: (Basu et al., 2015).

Figure 14 DSC curve for coconut fiber (Basu et al., 2015).

notably higher weight loss (49.1%) in the temperature range of 330–590 1C as compared to weight loss observed for raw (39.2%) and backwater retted (39.1%) fiber. The higher weight loss for the said region is indicative of the degradation of notably higher amount of cellulosic material present in chemically retted fiber. Chemically retted fibers are left with much less residue of 0.7% as compared to residue left in case of raw (2.8%) and backwater retted (2.6%) fiber.

4.9

Differential Scanning Calorimetry

Figure 14 shows DSC thermogram of coconut fiber. The relatively low temperature wide endothermic peak at 84.17 1 C is attributed to the evaporation of absorbed moisture and volatile substances (low-molecular-weight waxes and fats) of the fiber (Samanta et al., 2008). The second weight loss corresponds to hemicelluloses degradation at temperatures 241.01 1C (long). Degradation at 284.11 1C (small) may be due to pectin (Ali et al., 2009) and hemicellulose (Samanta et al., 2008) jointly. Among the two major constituents of coconut fiber, an endothermic peak at 364 1C is representative of cellulose degradation while, lignin, being the most resistant, shows an exotherm peak at 390.7 1C and its degradation still continued till 497 1C.

5 5.1

Quality Specifications Retted Coir Fiber/White Fiber

Retted coir fiber, also called white fiber, is extracted from green natural coconut husks after retting in flowing, circulating or changed water for a period of minimum 3 months. However, if the fiber is made out of pre-crushed husks the retting period could be reduced suitably. The fiber shall be free from moisture and impurities. Grading has been shown in Table 10.

18

Properties of Coconut Fiber

Table 10

Grading of retted/white coconut fibers

Grade

Color

Maximum impurities percent by weight

1 2 3 4

Natural Natural Natural Natural

bright light brown and/or light gray brown and/or gray dark brown and/or dark gray

2.0 3.0 5.0 7.0

Length of Fiber: The length of fibers shall be designated as follows: ‘Long’ over 15 cm. ‘Medium’ over 10 and up to 15 cm. ‘Short’ over 5 and up to 10 cm. ‘Bit’ up to and including 5 cm. Source: Quality specifications. Available at: http://coirboard.gov.in (accessed 22.11.15).

Percent by mass of ‘Long,’ ‘Medium,’ and ‘Short’ fibers and impurities in bristle coconut fiber

Table 11 Grade

Long Fibers Min.

Medium Fibers Max.

Short Fibers Max.

Impurities Max.

Bristle fiber Grade I Grade II

50 40

30 25

20 35

4 5

Source: Quality specifications. Available at: http://coirboard.gov.in (accessed 22.11.15).

Percent by mass of ‘Long,’ ‘Medium,’ and ‘Short’ fibers and impurities in Mattress coconut fiber

Table 12

Mattress fiber

Long/Medium Fibers Min.

Short Fibers

Impurities Max.

110

90

20

Source: Quality specifications. Available at: http://coirboard.gov.in (accessed 22.11.15).

Table 13

Percent by mass of ‘Long,’ ‘Medium,’ and ‘Short’ fibers and impurities in decorticated coconut fiber

Grade

Long Fibers Min.

Medium Fibers Max.

Short Fibers Max.

Impurities Max.

Grade I Grade II

20 20

30 25

50 55

7 12

Source: Quality specifications. Available at: http://coirboard.gov.in (accessed 22.11.15).

5.2

Brown Fiber

Brown fiber is mechanically extracted from the dry husks of matured and ripe coconut after soaking these husks in water. The fiber shall be free from moisture and impurities. Length of fiber: The mechanically extracted coir fiber shall be grouped based on the length Long fibers above 20 cm Medium fibers above 15 and up to 20 cm Short fibers above 5 and up to 15 cm Grading of bristle, mattress, and decorticated coconut fibers have been shown in Tables 11–13, respectively.

6

Conclusions

1. Property-based advantages of coconut fibers: • Resistant to fungi and rot. • Provides excellent insulation against temperature. • Not easily combustible. • Flame-retardant. • Resistant to moisture and dampness.

Properties of Coconut Fiber

2. 3. 4. 5.

6.

7. 8.

9. 10.

19

• • • •

Tough and durable. Resilient; springs back to shape even after constant use. Totally static free. Easy to clean. Coconut fibers are multi-cellular, lignocellulosic, hard, a very coarse, and rigid variety of natural fruit fiber. The quality of coconut fiber, depends upon agro-ecological conditions (rainfall, humidity, soil, etc.), variety of seedlings and most importantly on stage of harvesting and process employed for extracting the fiber. A good-quality fiber can be obtained from the green coconut husk when they are in naturally hydrated condition. The fiber at this stage found to be whiter, flexible, softer, and easy for chemical processing. Scanning electron micrographs of the raw fiber surface reveals cracks, voids, and parallel ridges, which are further connected with intermediate nodes perpendicular to fiber length, forming more or less rectangular indentation. The cross-section of fiber is circular having central lumen. Distribution of all the physical properties such as length, diameter, linear density, breaking tenacity, breaking extension, specific work of rupture, flexural rigidity, and specific flexural rigidity of the raw coconut fibers are of asymmetric nature with high coefficient of variation. Diameter of a fiber varies along its length with tapering shape at the both ends. Length, diameter, and linear density – three dimensional properties are positively correlated among themselves. All these dimensional parameters are positively correlated with breaking load and negatively correlated with specific work of rupture. Flexural rigidity is positively correlated with diameter and linear density. The major defects of coconut fibers are branched fiber, short and weak fiber, whereas, minor defects are coconut peat and mid-joint. Softening treatment of raw coconut fiber with combination of Na2S, Na2CO3, and NaOH decreases the flexural rigidity value of raw fiber by 75% without any deterioration of desirable properties viz., strength and elongation.

References Ali, R., Troedec, M.L., Peyratout, C., Smith, A., 2009. Comparison of the thermal degradation of natural, alkali-treated and silane-treated hemp fibres under air and an inert atmosphere. Journal of Applied Polymer Science 112 (1), 226–234. Balan, K., 2004. Coir geotextiles – An ecofriendly engineering material. In: Venkatappa Rao, G., Banerjee, P.K., Shahu, J.T., Ramana, G.V. (Eds.), Geosynthetics- New Horozons. New Delhi: Asian Books Pvt. Ltd., p. 365. Basu, G., Mishra, L., Jose, S., Samanta, A.K., 2015. Accelerated retting cum softening of coconut fibre. Industrial Crops and Products 77, 66–73. Basu, G., Roy, A.N., Satapathy, K.K., et al., 2011. Potentiality for value-added technical use of Indian sisal. Industrial Crops and Products 36, 33–40. Bhattacharya, G.K., Basu, G., Chattopadhyay, S.K., et al., 2009. Coconut Fibre and Its by Products: Present Status and Potentiality. Kolkata: ICAR-National Institute of Research on Jute and Allied Fibre Technology. Bhattacharyya, S.K., Paul, N.B., 1980. Durability of long vegetable fibers. Indian Textile Journal 91, 75–79. Brigida, A.l.S., Calado, V.M.A., Goncalves, L.R.B., Coelho, M.A.Z., 2010. Effect of chemical treatments on properties of green coconut fiber. Carbohydrate Polymers 79, 832–838. FAO, 2004. Jute, Kenaf, Sisal, Abaca, Coir and Allied Fibres Statistics (December). Rome: Food and Agriculture Organisation of The United Nations. FAO, 2008. Jute, Kenaf, Sisal, Abaca, Coir and Allied Fibres Statistics (June). Rome: Food and Agriculture Organisation of The United Nations. Goswami, B.C., Martindale, J.G., Scardino, F.L., 1977. Textile Yarns – Technology, Structure and Application. New York: John Wiley & Sons, p. 143. Hong, L., Zheng, P., Chen, Y., Chu., Y., 2009. Oxidation of flax fiber with sodium peroxide solution. Journal of Fiber Bioengineering and Informatics 2 (2), 120–125. Huang, Y., Fu, Y., 2013. Hydrolysis of cellulose 10 glucose by solid acid catalysts. Green Chemistry 15, 1095–1111. John, C.M., 1970. Coconut Cultivation, sixth ed. New Delhi: Indian Council of Agricultural Research. Kalia, S., Kaushik, V., Sharma, R.K., 2011. Effect of benzoylation and graft copolymerization on morphology, thermal stability, and crystallinity of sisal fibers. Journal of Natural Fibers 8, 27–38. Mahato, D.N., Prasad, R.N., Mathur, B.K., 2009. Surface morphological band and lattice structural studies of cellulosic fibre coir under mercenzarion by ESCA IR and XRD techniques. Indian Journal of Pure Applied Physics 47, 643–647. Manilal, V.B., Ajayana, M.S., Sreelekshmi, S.V., 2010. Characterization of surface-treated coir fiber obtained from environmental friendly bioextraction. Journal of Natural Fibers 7, 324–333. Massey, F.J., 1951. The Kolmogorov-Smirnov test for goodness of fit. Journal of the American Statistical Association 46, 68. Miller, L.H., 1956. Table of percentage points of Kolmogorov statistics. Journal of the American Statistical Association 51, 111. Mishra, L., Basu, G., 2013. Coconut fibre – Journey from food to fibre. In: Satapathy, K.K., Ganguly, P.K. (Eds.), Diversification of Jute and Allied Fibres: Some recent Developments. Kolkata: ICAR-National Institute of Research on Jute and Allied Fibre Technology, pp. 335–348. NRDC, 2009. Coco Lawn. New Delhi: National Research Development Corporation. Available at: www.nrdcindia.com/%20pages/cocolawn.htm (accessed 12.08.09). Pathania, D., Singh, D., 2009. A review on electrical properties of fibre reinforced polymer composites. International Journal of Theoretical and Applied Sciences 1 (2), 34–37. Rahman, M.M., Khan, M.A., 2007. Surface treatment of coir (Cocos nucifera) fibers and its influence on the fibers' physico-rnechanical properties. Composite Science & Technology 67 (11–12), 2369–2376. Rosa, M.F., Chiou, B., Medeiros., E.S., et al., 2009. Effect of fibre treatments on tensile and thermal properties of starch/ethylene vinyl alcohol copolymers/coir biocomposites. Bioresource Technology 100, 5196–5202. Rosa, M.F., Medeiros, E.S., Malmonge, J.A., et al., 2010. Cellulose nano-whiskers from coconut husk fibres: Effect of preparation conditions on their thermal and morphological behavior. Carbohydrate Polymers 81, 83–92. Samal, P.K., Rout, S.K., Panda, B.B., Mohanty, M., 1995. Effect of chemical modification on FTIR spectra: Physical and chemical behavior of Coir-ll. Journal of Polymer Materials 12, 229–234. Samanta, A.K., Basu, G., Ghosh, P., 2008. Structural features of glycol and acrylamide treated jute fiber. Journal of Natural Fibers 5 (4), 444–460.

20

Properties of Coconut Fiber

Sengupta, S., Basu, G., Chakraborty, R., Thampi, C.J., 2014. Stochastic analysis of major physical properties of coconut fibre. Indian Journal of Fibre and Textile Research 39 (1), 14–23. Sreenivasan, S., Iyer, B.P., Iyer, K.K.R., 1995. Influence of delignification and alkali treatment on the fine structure of coir fibres (Cocos nucifera). Journal of Materials Science 31, 721–726. Stern, F., Stout, H.P., 1954. Morphological relations in cellulose fibre cells. Journal of Textile Institute 45, 896–911. Tomlinson, C.H., 1950. Manufacture of alkaline process pulp. In: Stephenson, J.N. (Ed.), Pulp and Paper Manufacture, Preparation and Treatment of Wood Pulp. New York: McGrew Hill, pp. 364–381. Varma, D.S., Varma, M., Varma, I.K., 1984. Coir fibres: Part I. Effect of physical and chemical treatments on properties. Textile Research Journal 54, 827–831. Wei, W., Gu, H., 2009. Characterization and utilization of natural coconut fibers composites. Material Design 30, 2741–2744.

Further Reading Available at: www.coirboard.gov.in (accessed 22.11.15).