Otros acuerdos de los que dependen los pagos de intereses y del principal a los inversores

In the plastics industry, tonnes of reinforcements are used per annum, and there is a vast possible market for environment-friendly composite materials using natural fiber reinforcement.

Table 1  Fibers and countries of origin. (Source: Amar et al. 2005) Fiber Country of origin

Flax Borneo

Hemp Yugoslavia, China

Sun hemp Nigeria, Guyana, Sierra Leone, India Ramie Honduras, Mauritius

Jute India, Egypt, Guyana, Jamaica, Ghana, Malawi, Sudan, Tanzania Kenaf Iraq, tanzania, Jamaica, South Africa, Cuba, Togo

Roselle Borneo, Guyana, Malaysia, Sri Lanka, Togo, Indonesia, Tanzania Sisal East Africa, Bahamas, Antigua, Kenya, Tanzania, India

Abaca Malaysia, Uganda, Philippines, Bolivia Coir India, Sri Lanka, Philippines, Malaysia

P. P. Gohil et al. 56

Major source of natural fibers like sisal, jute, banana, and coir is grown in many parts of India and many of them have greater than 65 % aspect ratio. Sisal and ba- nana fibers have greater than 65 % cellulose and give comparable tensile strength, modulus, and failure strain with other cellulose rich fibers. These fibers are widely used for fishnets, matting, cordage, sacks, and rope, and as filling for cushions (e.g., rubberized coir). Cellulosed fibers are achieved from different parts of plants.

In polymer composites, plant-based natural fibers can be replaced to some level by more expensive and nonrenewable synthetic fibers like glass. Nangia and Biswas

Table 2  Composition of different natural fibers. (Source: Bledzki and Gassan 1999)

Component Cotton Jute Flax Hemp Sisal

Cellulose, wt.% 82.7 61–71.5 64.1–71 70.2–74.4 65.7–78 Hemicellulose, wt.% 5.7 13.6–20.4 16.7–20.6 17.9–22.4 10.0–14.2 Pectin, wt.% – 0.2 1.8–2.3 0.9 10 Lignin, wt.% – 12–13 1.7–2.0 3.7–5.7 9.9 Wax, wt.% 0.6 0.5 1.5–1.7 0.8 2.0 Moisture wt.% 10.0 10.0–12.6 10.0 10.8 11.0 Microfibrillar spiral angle (degree) – 8.0 10.0 6.2 20.0

Component Kenaf Coir Ramie Palm Henequen

Cellulose, wt.% 31–39 36–43 68.6–76.2 70–82 77.6 Hemicellulose, wt.% 21.5 0.15–0.25 13.1–16.7 – 4–8 Pectin, wt.% – 3–4 1.9 – – Lignin, wt.% – 41–45 0.6–0.7 5–12 13.1 Wax, wt.% – – 0.3 – – Moisture wt.% – 8.0 8.0 11.8 –

Microfibrillar spiral angle (degree) – 41–45 7.5 14.0 –

Table 3  Properties of some synthetic and natural fibers. (Source: Saeb and Jog 1999) Fibers Tensile strength

(MPa) Tensile modulus (GPa) Specific gravity Specific strength Specific stiffness

E-glass 2500–3500 70–73 2.56 27 29 Carbon 2500–6000 220–700 1.75–1.9 116 400 Flax 500–900 50–70 1.4–1.5 33 50 Sisal 80–840 9–22 1.3–1.45 6 17 Jute 200–450 20–55 1.3–1.4 14 42 Hemp 310–750 30–60 1.48 20 41 Banana 530–750 7–20 1.4 5 14 Coir 130–175 4–6 1.15 3 5 Cotton 300–600 6–10 1.5 4 7 Silk – – 1.34 – – Wool 125–200 – 1.31 – –

Natural Fiber-Reinforced Composites: Potential, Applications, and Properties 57

(2009) showed that the maximum tensile strength (jute–epoxy), impact strength (jute–polyester), and flexural strength (banana–polyester) is 104.0 MN/m2_{, 22.0 kJ/}

m2_{, and 64.0 MN/m}2_{, respectively.}

Several countries have devoted themselves to the Kyoto protocol, whereby a reduction in greenhouse gas emissions (mostly CO₂) have to be compacted to levels under that of 1990 among the years 2008 and 2012. Pervaiz and Sain (2003) il- lustrated that, by using hemp fiber and other natural fiber in place of glass fiber in composites, 3 t CO₂ per tonne of product can be saved (Fig. 3).

The mechanical properties of natural fiber composites depend on parameters like fiber strength, modulus, fiber length, and orientation in addition to the interface strength. In the natural fiber composite properties, fiber–matrix interface plays an important role. For effective load transfer, a good interfacial bond is required. In ad- dition, it improves moisture resistance and the composite properties. The modulus of elasticity of the fiber should be higher than matrix for effective reinforcement. The mechanical properties of unidirectionally aligned continuous fiber composite with polyester resin along with randomly oriented short fiber composites are given in Table 4. Sisal fibers show a very good impact performance with specific impact strength similar to fiber-reinforced composites and show the most balanced me- chanical properties. Coir presents as high a strength as jute and banana fibers with respect to tensile and impact strength of composites. Table 5 shows different proper- ties of cotton fabric–polyester composite (Wiley 1955)

Gohil and Shaikh (2007) developed cylinders of varying thickness (3, 5, and 7 mm) with cotton fiber and polyester resin using the filament winding technique on lathe machine which are shown in Fig. 4. The hydro test and some weight study were also carried out. At the same time, the polyvinyl chloride (PVC) shell of the same dimension was also tested and a comparative study was carried out.

Mussig (2008) compared the cotton fibers in composites to ramie fibers. By us- ing a Dia-Stron device, the strength of fiber was tested and the testing of fineness was carried out with fiber shape. Cotton- and ramie-based composites were pre- pared with epoxy resin and a bio-based resin. The results of tensile and impact tests show that mechanical properties of the composites strongly depend on fiber proper- ties. Cotton with its morphological and mechanical properties can play a more vital role to optimize products with a view to improve the impact properties.

Fig. 3  CO₂ emissions per tonne of composite, and reduction in emissions by substituting glass fibers with hemp fibers. (Pervaiz and Sain 2003)

P. P. Gohil et al. 58

In India, approximately 1.5 million acres of land is cultivated with banana plan- tations, which yield about 3 × 105 _{t of fiber (Kulkarni et al. 1983). It has been noted}

that banana fiber has been substituted for asbestos in bitumen and can be used for roofing (Satyanarayana et al. 1990); also, banana fiber/polymer composites and cot- ton fabric/polyester have been used in cars and for bearings, respectively (Satyana- rayana et al. 1990).

Table 4  Mechanical properties of unidirectionally aligned continuous fiber composite with poly-

ester matrix along with that of randomly oriented short fiber composites. (Sangeeta Nangia and Soumitra Biswas, TIFAC)

Fiber (wt.%) Tensile

strength (MPa) Modulus (GPa) Flexural strength (MPa) Flexural modu-lus (GPa) Impact strength (kJ/m2)

Unidirectional Sisal (40) 129 8.5 192 7.5 98 Banana (30) 121 8.0 – – 52 Coir (30) 45 4 56 4 44 Chopped random Sisal (25) 34.5 1.9 86.4 – 30 Banana (25) 43.5 2.3 92 – 10 Coir (25) 14.0 1.4 31.2 – 11 Fabric Banana–cotton 27.9–35.9 3.3 50.6–64 – 3.1–7.5 Fig. 4  Cotton–polyester

cylinders (Gohil and Shaikh

2007)

Property Value

Density (kg/m3_{) 1400}

Tensile strength (MPa) 34.5–68.96 Flexural strength (MPa) 62.1–124.1 Modulus (GPa) 2.76–4.14 Impact resistance (kg m/m2_{) 253.3–428.8} Table 5  Properties of

cotton fabric–polyester composite. (Source: Wiley

Natural Fiber-Reinforced Composites: Potential, Applications, and Properties 59

Satyanarayana et al. (1984) prepared banana fiber composites with 25 % wt frac- tion by hand lay-up method and weathering tests (ASTM D570) were carried out. It was observed that the specific modulus was around 2.39 GPa and impact strength was about 10 × 103 _J/m2_{. After weathering tests, reduction was observed in modulus,}

ultimate tensile strength, and flexural strength around 8, 13, and 26 %, respectively. Satyanarayana et al. (1981,1983, 1986) included banana fiber in the weft di- rection and cotton in the warp direction with polyester resin in different weight fractions (9– 25 wt.%). It was observed that up to 14 wt.% fabric can be included by way of a hand lay-up practice with no pressure. Mechanical properties of these composites have been estimated and are shown in Table 6 (Mohan et al. 1983). Geethamma et al. (1998) anticipated the persistence and modulus of elasticity of banana fiber within the range 529–759 MPa, and 8–20 GPa, correspondingly. The percentage elongation at break of fiber varied from 1.0 to 3.5. Banana fibers are stiffer and stronger than sisal fibers (Fig. 5).

Sapuan et al. (2006) carried out the tensile and flexural tests. They prepared three samples from woven banana fiber composites with different geometries. It was found that the maximum value of stress in x-direction and y-direction is 14.14 and 3.398 MN/m2_{, respectively. The elastic modulus was 0.976 GN/m}2 _{in x-direction}

and 0.863 GN/m2 _{in y-direction. To get the deflection of woven banana fiber speci-}

men beam of 0.5 mm in flexural test, a load of 36.25 N was applied. The maximum stress and elastic modulus in x-direction was recorded to be 26.181 MN/m2 _and

2.685 GN/m2_{, respectively. They used one-way analysis of variance (ANOVA) for}

statistical analysis and showed the variations of results obtained from samples are insignificant. Sapuan et al. (2001, 2003) have also performed an experimental study for epoxy/coconut shell fiber composite.